So the most likely cause of the limping is a muscle sprain. What is recommended in her case is just to rest her for now! Restrict her activity as much as possible for the next week. This can be tough because pets don't know they should take it easy! So what you will want to do is when you aren't able to directly watch her, she should be in a kennel/pen/small area so she cannot run around. Carry her up and down stairs, no jumping on and off furniture, counters, etc. SHe should not be allowed outside if she is an indoor-outdoor kitty.
If you have any sense of the area of the leg which may be bothering her you can also apply an ice pack (always be sure to put a towel or blanket around the ice pack so it isn't directly touching the skin)- a bag of frozen peas works well for this. You can put it on her leg for 10 minutes, a few times a day. If she fights this, then don't bother because her struggle will just make it worse!
If she seems very uncomfortable and can't sleep at night, then I would call your vet to find out about getting a safe pain reliever for her. Unfortunately there are not any safe over the counter pain relievers for cats and many are toxic to them, so don't try to give her anything from your medicine cabinet.
If after a week of rest, she is still limping, or if at any point you do notice swelling, or she becomes MORE painful, then these would be reasons to take her in for an exam and possibly an x-ray.