I think you did the right thing by communicating with your

boss, if I were you, I'd

1. cancel her work from home

2. provide training only on the as needed basis, bottom line no more previleges for A

3. 1 on 1 with A, tell her that you had a meeting with your boss in regards to her comments about your team and yourself, see what she has to say. Make it very clear that her behavior is unprofessional and not acceptable.

you need to be firm with her, no one is irreplaceable.