What are the long term effects of water fasting for 19 days?

It’s hard to get a scope online about such a thing, it’s hard to trust chatGPT either

I have a girlfriend, 22, she told me she did a water fast for 19 days before her baptism when she was 18. She’s now concerned that she has a lot of issues, memory troubles, vitamin deficiencies, trouble with her bladder.

I’ve tried explaining to her that such an extreme fast could be the reason for these problems, she’s basically denying it as the problem.

Could somebody with knowledge of such things or experience please tell me if this could be the result, what that level of fasting could do to somebody permanently, what is reversible and what is irreversible. She told me she had nothing but water during that time and reintroduced herself to food slowly after the fasting ended.