Well it is very vague what you are concerned about going on.
If it is something you are truly worried about, you need to address it with the provider immediately.
Coming from a home care provider myself, I have a very open forum with my parents, if something went wrong here (even for every time out) they are told when they pick up their child even if it is petty so they are aware, vice versa, if they have concerns they come to me.
I truly believe if it is something big you are worried about then you have to figure out what is truly happening sooner then later. You can tell if the provider is going to make excuses, hiding the truth, etc.
2 1/2 year old have huge imaginations. Playing with other kids they pick up on stuff really fast, however, they are also pretty honest so I understand your problem here.
If you trust this woman to watch your son,you should feel comfortable finding out what is going on. Even calling some of the other parents that she works for and asking them if they have had issue. Don't just assume what your son is saying is right, you are correct that they can sometimes mixed up the facts, but your gut instinct is something that should always be followed.
If you find out she is not doing things the right way and children's safety are on the line, she is licensed go to the county/city she is licensed in and file a formal complaint so it can be investigated. You can also check with the county/city to see if any other complaints have ever been filed on her.
Good luck, I hope it all works out.