Sometimes, some guys don’t know they’re being unrelational, they don’t know they’re making a girl feel awkward, they haven’t picked up on the normal social cues. They’ll trap a girl (or a pair of girls) in a conversation after church or whatever…
So, guys, love your sister and go and interrupt. Go and offer them a drink, ask if they’ve seen someone your looking for, anything. It gives the girl an out; an opportunity to politely excuse herself from the awkward conversation.
It may not have been awkward, and you might make it awkward by doing that… but that’s better then leaving a girl trapped.
Then, afterwards, train her in dealing with socially awkward guys.