I'm a dude, but learned a lot of restorative techniques in martial arts. There are two that work exceedingly well for menstrual cramps. This is going to be difficult to explain in writing without a demonstration, but I'll do my best. I've done these many, many times for my girlfriends in the past, wife, sister, mom, aunt, etc., it works extremely well:
Technique 1: Simple to do, fast (about 1 min), can be done on yourself, works almost always:
Take your first three fingers (index, middle, ring), side by side, and place them just above your inside ankle bone. You will use these three fingers as a measure. The distance of your three fingers up from the top of your ankle bone will land an inch or two above your ankle bone, on the inside of your lower leg. On that EXACT spot, apply a little pressure with your thumb, and increase the pressure slowly until it becomes painful. You want to take as much pressure as you can tolerate, then slowly release the pressure. Do this three times.
Now, you will have a 50-50 chance of having picked the right leg. If you picked the correct leg, your menstrual cramps will/should be gone. If not, you will have to try the other leg. Whichever is the correct leg will hurt much more when you press on the pressure spot, it will be very sensitive, so this is a good way to tell which is the correct leg. It will alternate each month, as your ovaries switch each month. You will also be able to tell if you are hitting the correct spot by whether or not it hurts -- if it doesn't hurt, you have not accurately located the spot.
Technique 2: Takes longer (10-15 minutes), need someone else to do to you (massaging the back of the leg), works always:
Same thing, as above, you have to pick the correct leg. In this technique, you massage the back of the calf, on the outside. The "patient" should lie on their stomach. The person doing the massage will start at the ankle, and massage up the calf, rolling their thumb firmly along the calf muscle and working up the leg to the back of the knee. Start with one pass towards the middle of the calf, then work up again a little more to the outside, then again so you're on the side of the calf. There should be a little discomfort from this massage, if not then it's not being done firmly enough. Do this three times, three passes up the leg, and the cramps will be gone. Do the other leg if you've picked the wrong one. Again, one leg will be noticeably more sensitive than the other.
A great thing about these techniques is they are extremely reliable. At least one of them has always worked in the past when I've done it to others, and others in my training noted the same experience. Also doing it once tends to stop cramps completely for the rest of your period, you don't have to keep repeating it (i.e., you do it once at the onset of cramps, and you're likely done until next month).
Feel free to post questions if my description was not good enough, it would be much easier to demonstrate!