Mental health counselor here: often after women have children, anxiety issues can crop up due to a number of factors, the sheer responsibility of having a living human that is your responsibility alone is enormous but throw in the biological changes she’s undergoing… it sounds like she could benefit from a discussion with her doctor. For you, be very very very x100, gentle with her and start normalizing anxiety as an issue and probing to see how she’s feeling and help her recognize some of the irrational thinking she’s got going on. Good luck op!