I in she used to always stare at me and why?

This girl that works at my local pet store age 19, used to always stare at me whenever I'd go into the shop.
I'm 24f
I would always notice this and thought she looked sweet and wondered why she'd stare?
Not so long ago she was asked by the manager to help me out with something and I was pleased she actually had to talk to me. She was very nervous I noticed because she talked super fast but I don't know if this was just social anxiety?
I plucked up the courage and added her on Facebook and also engross in conversation with her at the shop when I go there every so often.
She's really awesome and we have tons in common. She always smiles and once when I was leaving she was staring and smiling as I left.
Last week she got into a relationship with a guy she just met.
I'm still curious as to why she used to stare ? Any ideas ..
She's really helpful and kind!
If I need help with something she seems to go out of her way to do it. She seems good natured :)