Ok, I'm almost certain the shirt is in Chinese. The first and third kanji are 超 and 子 which would probably mean "Super ___ girl" (correct me if I'm wrong). The second kanji is partly obscured, but almost certainly contains 宀 and 卩 as radicals from what I can see. According to the kanji dictionary that leaves us with {婉, 宛, 椀, 碗, 腕, 蜿, 豌, 鋺}. Of which only 腕 "talented" makes much sense, but it doesn't really look like it should fit given the spacing. There is a transcription below (also obscured) which I don't know enough about chinese enough to match up, thoug it looks like the first and third Kanji match "chao" and "zi" for mandarin. Anyone with better Chinese or Kanji skills than I up to verify or correct?

It says 超包子 ("chao baozi" in Chinese, "chou paozu" in Japanese), which, according to a quick search, is the name of the food stand she runs. The other note is also wrong.

It's 超包子 "Chao Bao Zi."
It's apparently a fictional fighting style related to the character wearing the shirt.
http://en.wikipedia.org/wiki/Chao_Lingshen

Ignore what I said about it being a fighting style, I saw the word "stand" in wikipedia, and thought it said "stance."

Ok, that makes sense. I never realized she ran a ramen stand.

Based on the series she's from (Negima!), and the Del Rey manga translation of it, the shirt should say "Chao Bao Zi". That, coincidentally, is also the name of the restaurant that the girl is one of the operators of.