I guess there could be many reasons why she's not winning matches. Professional sport is brutal, and the margin between success and failure is very small. She doesn't have to b
I'm just speculating, of course, but as you said, sports athletes usually don't write negative or depressing things on their twitter accounts. With few outrageous exceptions, it's not supposed to be a vent for stuff like that.
It's part of an athlete's job to have an ego that's somewhat in denial. Serena Williams is the supreme example of this in women's tennis. She will make up any excuse in the book as a reason for why she did not play well in a match, to avoid facing the reality that her opponent played better. Players will always make public statements limiting the damage, minimizing the negative and maximizing the positives, any time they lose. They have to, otherwise, what would be the motivation to continue playing? Even though her record is 2 and whatever, Tamira is going to find positives when she plays a tight three setter, because it's better than usual. That doesn't mean it's great, though.
But as for Tamira, at this point, the self-belief on the court doesn't look like it is there. Where it came from, where it has gone, where she can get more of it, those are the questions she has to find answers to, because right now, she looks like she is doubting herself on the court. Many times, self doubt and lack of confidence relates to self-esteem. When people are feeling happy and secure in their lives, they tend to doubt themselves and what they are doing a lot less. Maybe I have no clue what I am talking about in her case, but in general, it usually works out that way.
Now that her ranking is low, I hope she comes to the USTA Pro Circuit next winter/spring and plays some events here, until she can bump her ranking up. I'd definitely go see her play and cheer her if she came to the Florida events.