the shift after dark

i met this girl last week who came in late nights when i'm working at the bar... and yeah things got a little wild for a couple hours. we kept it all secret though, because i have a good relationship with my long-term partner, even if it's not always perfect. one night she was there and after a few drinks and chatting, we kinda just leaned in and kissed behind the counter... then moved to a back room. it wasn't planned or anything, but the moment felt right. i feel bad about it though, because she’s never acted on it since. wondering if i should confess this to her or just leave well enough alone....