Most Helpful Girl
If you are really 25-29 and in school (working on a masters or doctorate ) you should be more intelligent. It IS creepy to just text "what's up?" Text with purpose. Ask her out or ask a valid work/school related question. My guess is;
1) You've lost your shot at this girl.
2) you are not 26-29
Most Helpful Guy
She probably has something going on in her life right now, and to be honest, trying to predict what a teenage girl is thinking is like figuring out a way to walk on the sun.
Just so you know in the future, when a girl gives you her number, you text once and only once and see if she responds. If and when she does, don't start the next convo, let her do it. You need to let her start the convos sometimes, else she'll just get bored and think you're desperate, even if you're not. My brother does this all the time and I try to tell him, but he won't listen.
Also, unlike my brother, don't text her all day, everyday. It's ok to end conversations sometimes; give yourself a little mysterious look if you want to put it that way.
tl;dr Sometimes start convos and sometimes end them. This way, work load is equalized and no one looks desperate or gets bored.