You are a regular there. She knows who you are. She probably never noticed what your shirt said. She may have been just being friendly to a regular customer, getting to know you better. She may be attracted to you and trying to start a more meaningful conversation with you.

You gave really short replies, when you could have opened the conversation up to more.

C'mon, you're in IT Development and she is a barista who wants to know if you need education to do what you do-- just warm up and ask her out already.