That is a brutal situation.

Once we start commenting on people's husbandry, they tend to get very defensive. They take it as a personal attack. The moment you make suggestions, they'll bristle and tell you that they know what they're doing and get mad at you. They'll tell you to get out.

Why?

This exact same thing happened to me. I was asked to come over and babysit a friend's reptiles, and they were in awful condition. The subadult beardie was in an 18" x 18" x 24" exo terra. He had to sit facing a corner just so his tail wouldn't be propped up against the glass. The Leopard gecko was in the same sized exo terra and had only one hide. It was just bad.

When I approached her on the topic, just really mildly, such as: "While you were gone I fed your beardie some veggies. He really loved them. Maybe you could keep up with feeding him veggies, since he loved them!" This was met with: "You fed my beardie new things without my permission?! I gave you pellets to feed him. How dare you make any choices without my approval. I don't care if he likes them! Veggies are bad for beardies!! Gosh you know nothing. I should've never let you babysit!"

It was awful.

And there was nothing I could do to change it. I tried approaching her mildly, friendly, then more assertively, then almost aggressively (telling her that her beardie was going to die a horrible death if she didn't give him UVB and feed him a varied diet instead of just pellets).

Nothing changed.

That was, until I got a phonecall.

"My beardie is having a seizure and I don't know what to do!" I calmly informed her that she had told me not to give her advice anymore and that I warned her her beardie would die without changing it's set-up. Said I wouldn't help her unless she promised not to cut corners anymore and actually listen to suggestions. While crying, she agreed to listen and make changes.

It took her animal almost dying in front of her to realize she was wrong.

And unfortunately, just a few months later, the care reverted again and she got rid of her reptiles. Some people just aren't meant to own animals. Period.

So I can't give you advise one way or another with this, because every situation is different. however, if you feel that this person isn't a close friend, I wouldn't be afraid to stand up and be assertive in this situation. It might not work, but at least you can give her the warning that her animals WILL die and WILL suffer if she doesn't change. And only she controls that.