Self diagnosing a child

My SO'S ex wife has been rambling on about their 5 yr old having anxiety. She keeps telling their daughter her belly aches are due to it, and this kid already is a major hypochondriac.

She has never taken her to the doctor (nor have we) to have her evaluated. I really feel like this could be detrimental to their daughter and hindering her even more (giving her an excuse to not try new things). Why tell a child there is something wrong with them when they are actually completely normal? She is seriously super happy, or as much as a kid could be for having their parents divorce.