I'm not flirting with your boyfriend because I touched his hand

I work a customer facing role and so the vast majority of my job involves interacting with customers.

I've had my fair share of dirty looks from girlfriends because i'm interacting with their boyfriend (aka doing my job).

But this week I had someone actually laugh in my face because my hand momentarily touched his to give him his change.

From the minute they came over to the till and I greeted them she was giving me evils. Her boyfriend was the person ordering so naturally I had to speak to him. She continued watching my every move the entire interaction and as I passed him his change she went "uhh" laughed and then walked away.

The best/worst part about it is i've known her since we 2 and we're friends for a while too.

I promise you me handing your boyfriend his change or talking to him is not me flirting with him. I'm doing my job.