Try talking to her calmly one night and ask her how she is feeling on her meds. Ask her how she feels about you as well. You can try to figure out if she needs a different medication or if she needs marriage counsoling becauase of something with you. That would mean you and her need counsoling not just her.
Not all women are like that. I am on medication and I don't get angry at my husband out of the blue. She could have an issue in the marriage like a decision that wasn't totally hers that she didn't like and she is getting even by snapping at you for little things. Anyways, it will help if you talk to her about it.
Good luck.