Ok, this sounds kind of like when my best friend, LJ, and I went boxing together. She had been boxing for 2 years and it was my first time boxing. She offered way too much help for my liking, she stopped me after every single punch and yeah I got angry even though I know she was only trying to help me. I wasn't angry at her, I was angry at myself for not getting it right and the constant help kept reminding me of exactly how wrong I was getting it.
Your wife may just need some time to practice on her own and find her feet again. I know if someone gave me a punching bag instead of a partner I would have been a lot happier at first and then would have the confidence to work with LJ later on.
BTW: I apologised to LJ for getting angry and I haven't been boxing since. I also coach squash so I have been on the recieving end as well, it's not nice but it happens.