how can i show my appreciation? should i even?

i like this a lady who works at a coffee shop i've frequented over the years. i like her, and i don't know what to do about it. i wouldn't feel as bothered by this if i didn't think i had the slightest chance with her. it's because there's a possibility that i find it difficult brush it off. i think to myself "is she this nice to everyone or just me" and then i think it's because she's at work yada yada and no you're obviously imagining things.

i'd like to show her my appreciation, but then again i don't want to make her feel uncomfortable. then i wonder if she actually enjoys my presence and feels disappointed whenever i leave. that thought really bothers me. in my mind it's 95 % i'm delusional and 5 % she could actually be interested.