Assorted thoughts (fellow horse person here):
Here are 3 of the main things that seem to motivate us:
- loving to compete -- like any sport
- loving the relationship/team aspect of the sport, working with/training a particular horse over time
- loving caring for horses and their environment/gear
Not mutually exclusive but my observation is that most of us are much more motivated by 1 or 2 of those items rather than equally by all 3.
Your GF wants to compete and improve. What does improvement mean to her? It matters (and is worth thinking about). Given that she's taken on dressage, she might want to move "up through the ranks" and compete at successively higher levels, or do successively better. She might "need" an expensive horse to do this (and as others have noted it's not really the "cost" of the horse in a purchase-price sense, it's everything that goes along with that), depending on what motivates her (see above) and at what level she wants to compete. But there are other ways she can ride and improve, in measurable ways.
Here's a hypothetical: let's assume your GF owns a lovely 8 y.o. warmblood (we'll call him Bob) and is currently showing successfully at 2nd level. She works hard, and 2 years from now she is showing him successfully at 4th level and eyeing a move to Prix St. George. Tragically one night Bob colics and dies. Of course she is heartbroken. But she still loves to ride and fortunately she had good insurance and has some funds available to buy a new horse. Not a "replacement" for Bob, not emotionally, of course, but also not in terms of level of experience/training. She's going to have to backtrack somewhat. There are 2 really good prospects her trainer has recommended to her. One (Joe) is Bob's full sibling, almost a carbon copy. He's 8, and also showing second level -- so sort of a rewind. The other (Harry) is Bob's half sibling, same age, same level. But he's half thoroughbred and a very different sort of ride. She figures it will take her at least 6 months and more likely a year to get used to Harry and start to move up through the levels, whereas she could hop on Joe tomorrow and be showing 4th level again -- presumably -- in 2 years.
What does she choose? Joe will give her the easier "measurement" of her "improvement" (though either way she's repeating stuff, just as every marathon a marathon runner runs is in part a repetition of the last one), but I'd argue Harry will actually offer her more chance to "improve" (even if in ways that no one will be exactly able to quantify).
I've owned horses over the years, my last one died (colic -- and yes, I paid for surgery, OOP, and no, it didn't work) 4 years ago and I haven't replaced him. I loved that horse. But I needed a horse like I need a hole in my foot (or wallet). Now I ride for free by borrowing friends' horses. I've done this a lot (also as a teenager, when I could ride anything with 4 legs, broke or not. I'm older and more sensible now, but I can still ride a ton of different types/levels of horses well.). If you're a decent rider who shows up when you say you will, it's very easy to find free rides -- lots of people own horses they want ridden/trained but don't have the time to ride them, and when you're borrowing horses, you can really take your pick -- green, lame, crazy, or any combination of those 3 attributes. I'm kidding -- partly. I mostly go for lame.
That sounds horrid, but lots of lameness problems are actually fitness problems. I'm not really riding lame horses. I ride 2 -- a retired Intermediate event horse, and a draft/TB cross. The retiree
is bordering on lame (arthritis) and I have to be careful with him, but I'm pretty sure what I do with him isn't only improving his immediate well-being (when I ride him, starting gradually over time by getting him fit by walking up hills, he goes from lame to sound) but also extending his life span. The draft/TB cross started out really, really short behind -- stifle problems -- and was himself basically semi-retired but now carries himself freely and forward with a nice soft topline and doing lovely training level/first level dressage (not much of a trot lengthening, at least not yet -- he's got the shoulders of a Clydesdale). I'd argue that getting him sound and moving well has actually been more challenging than showing a nice warmblood (or TB) even if it doesn't come with the same flash and external recognition.
(I ride in the owners' saddles, or 2 old saddles I already own, buy a new cheap pair of tall boots about once every 2 years, and pay for gas to the barn. I'd guess I'm spending $15/month to ride 4 times/week).
Dressage is something that all horses can benefit from (think Pilates for horses...), and there are plenty that aren't naturally good enough "movers" (as seen from the competitive dressage perspective) that anyone wants to fool with them.
I know this place is "all about" RE and some of that's premised on the fact that when it comes to saving, time is your friend. Use compounding, work hard young, save, and have the rest of your life to do what you want. But there are things that don't lend themselves (nearly as) well to being done when you're older as when you're younger and I think that often gets glossed over in the RE excitement. Some types of travel, particularly if you're otherwise inclined to bog yourself down with things like home ownership, a spouse, and kids; having kids, particularly for women; and lots of athletic endeavors.
Particularly taking time (truly) away from riding does not, in my experience/observation, bode well for our continuing to do this, or do it well, as we age. It's a silly example (because so extreme), but if you and your GF were lots younger and she were a (legitimately) aspirational Olympic gymnast, no one would dream of telling her she should "just work until she's 40 and then retire to pursue her gymnastic career."
OTOH even one month without owning a horse would save your GF $1K. If she already owns a horse, that doesn't help much; I'm assuming she doesn't want to sell the one she has. But it's certainly worth considering whether cutting back now (e.g. by borrowing rather than owning) is something she can do while still finding ways to enjoy the sport. And it's not at all a lifetime commitment (to non-horse-ownership or whatever other downsizing route she considers). Believe me, if she keeps even one toe in the horse world, she does not need to worry that people won't be keeping an eye out for horses she might want to buy, or encouraging her to reconsider jumping back in to horse ownership :) . There's a lovely little off-the-track TB out where I ride who's the spitting image of the horse I lost and who's been bought there to be trained and sold and plenty of friends have suggested it's time for me to get back into horse ownership :).
GL.