I think she suffered from anorexia or bulimia (one of the two) and was in the hospital for a couple of years. She just started to make a comeback to pro tennis this year and has had some decent results. She'll never be a big name, but she could get back to the top 200 ranking she had before her illness.
As to why she never really made it, Lenka doesn't have a big weapon. She's basically a Serra-Zanetti clone.