Anti-biotics have their purpose. Usually when we over do them is when trouble occurs.
I took anti-biotics a few times as a kid with no issues. It wasn’t until I took 4 different kinds everyday for a few months did I get Candida.
How long is she going to be on the anti-biotics?
Keep pushing her to eat yogurt & kefir and that should be enough.
I would check with your doc about the pro-biotic capsules for kids.
It’s also most important to keep her eating the yogurt and kefir for weeks AFTER the coarse of drugs.
Gook luck and hope everybody feels better.