[ Singles & Dating ] Open Question : My GF works full time, but is stingy with her money?

She works M-F 8 hours a day 12/hr. She only pays for her cell phone bill and gas, her mother pays for the rest. She's a part time student. I on the other hand am a full time student and i don't work. Last night what bothered me was we went to Disneyland for my sister's birthday, my GF's ticket and dinner was paid for by my other. At the end of the night she didn't even offer to buy me ice cream which is an easy $4 or offer to buy ice cream for my family and my sister's bf, there was 5 of us total. She offers to buy me coffee sometimes which is $2.50, but other than that she never offers to pay for our dinner. When we do eat out we pay separate which is good. I only treat her out for dinner once a month on our anniversary. Yes my gf is stingy, but do you guys think this is too stingy. It gets annoying sometimes.