Well, this is a difficult thing to translate. I don't exactly agree now with what I wrote 14 months ago, and since that time 'college' and 'university' have been added.
Basically, the Polish sentence means that she thinks about something connected to her university education. Maybe she's in high school and she's thinking about her future. Maybe she is already a student and she's thinking about the test next week and the essay that's due tomorrow. Maybe she is thinking that she made a wrong choice choosing her major and wonders whether it's too late to change it. Maybe she is 35 and just thinking about the good ol' times. Basically, it's a university equivalent of a similarly vague "She is thinking about school".
'szkoła techniczna' may be a part of the name of some university focused on technology, but my first (wrong) thought was that it's a 'technikum', so clearly that's not common.
'szkoła wyższa' is a very general notion for an institution dealing with university education, it can sometimes be a part of a name.
How to put the American notion of 'college' into the Polish context, I'm not really sure. This idea and how it's different from 'university' has always been confusing to me.