In dealing with living with parents:
It sounds like mostly mom is the issue here?
Assert yourself as a grown up. As in:
"You know, Mom, I understand you're concerned for me and just looking out for my wellbeing, but I'm 23 years old and where I'm going is really none of your business."
"Thanks, Mom, but I don't have time to help you with your errands - I have some things I need to work on today. What are they? None of your business."
"I'm happy Aunt Juanita and Uncle Ben are in town, but that's not what I had planned this weekend. Have fun with them!"
Luckily, when I lived with my mom as an older teenager and young adult, she pretty much kept out of my business, with a "If it isn't going to kill you, you'll be ok and it's none of my business" policy, which I really appreciate. I just wish she was better with her money, because then I (and my husband!) would still live with her.
If it really comes down to it, and she continues to horn in on your business, let her know the truth: "I'm not a kid anymore, and I don't need your mothering, I just need your friendship. I'm only living here to save for my future, and I appreciate the opportunity. Don't take that away by treating me like a teenager."
"I'm an adult now, and I don't need you to plan my free time anymore. Maybe you can plan your free time instead. Have you thought about a spin class?"
In dealing with coworkers:
This just depends on how aggressive you want to be, and how much of your privacy you want to retain. When the 27 year old with a BMW starts giving you crap, ask them how much money he's saved. Ask them how much their rent costs over a year. Tell them you saved 40k in the last year and plan on buying your first property in cash (or putting 50% down or whatever). Ask them what their retirement account looks like.
When your family gets pointed with you about "moving on", explain how far ahead of your peers you're going to be by not having to pay rent.
Or, smile politely and say, "This is what works best for me right now."
Just own yourself, don't let anyone else's opinion own you.
In dealing with the Boyfriend:
Although you're very mature with your money and career, there are some things that just come with living by yourself and being responsible for your own space. I mean, I may be married and moved away from my parents, but the lady I live with still takes care of all the cleaning, so I'm not exercising those skills. I don't clean my own bathroom or remember to buy toilet paper, because those are perks of paying my rent. Eventually, when I move out, I'm going to have to tackle those things - I'm going to run out of toilet paper because I'm not used to being the one that buys it.
"You might be too reliant on others" might mean "I'm afraid to be stuck being the responsible one."
In fact, it's very similar to a conversation I had with my husband before we moved in together, since I didn't like the idea of him moving out of his family's house into my mom's house without ever having to clean his own toilet. It's part of why we keep separate finances - He needs to see that it's sink or swim, budget or drown in debt. I want to make sure he's got it together, that way I don't have to have it together for us.
Once again, this is a situation where you have to own yourself. If YOU know you're responsible, does it matter what he thinks? Do you want him to propose before you're 25? I mean, you could propose. Do you want to be that attached to someone that doesn't see the value of the savings over the novelty of living alone? Or, maybe next time your answer should be, "Well, how's breaking up with you for not relying on others, huh?" Show that sukka.
Alright, I think that's enough of my two cents. :)
Good luck!
PS:
I would go crazy living with my parents at that age. You can always rent a room somewhere for probably $500/month with a friend to give some balance and freedom in life. If you currently save $40K/yr then spending $6K a year in rent for your sanity/freedom would only push out $100K goal by 3 months.
+1 to this argument.