New trend in tipping

[c&c1913]

I was wondering if anyone else has experienced this situation (I'm sure you have) and how you handled it.

Situation:
I was at restuarant with 3 people the other day. The check comes. Of course the waitress puts it all on one tab. Her service was okay, but not outstanding. We look at the bill and pay our share. I don't remember the exact total, but is how it breaks down:

Me- My change should've been $10
girl B- change = $5
boy A =$10
boy B- pays with a debit card, but adds $5 for a tip.

She brings boy B's receipt and then asks us if we wanted our change? We decide to let it slide and not act a fool.

My question is this: How is she going to ask us if we wanted something that belongs to us anyway. I know servers don't make much, but she just designated herself a $30 tip and I don't think her service warranted it.

What would you guys do?