Use 'nip off' when someone leaves a place swiftly, often without drawing attention. She nipped off after the meeting before anyone could ask for her help.
Pro Tip 2/3
Slight Politeness
'Nip off' can feel less abrupt than 'leave', showing a bit of courtesy. I need to nip off now, but thanks for the wonderful lunch!
Pro Tip 3/3
Casual Context
Best used in informal situations; might be too casual for formal events. Hey, I'm going to nip off to grab a coffee.