Its really hard to predict the outcome here...

I know several guys who have had threesomes in long-term relationships and they were shot to hell immediately after... however in all cases it was the guy who asked for it and the girl wasnt really into it but went along because she was trying to please him... BIG MISTAKE.

I think more dudes need to think about the situation in reverse. Think about how you would feel if your girl asked you for a threesome with another guy. Do you feel good that she is blatently admitting that she wants to get plowed by another guy? Would you be happy watching that happen?

Generally, a threesome should only happen with randoms who arent important. However in this case she did ask for it herself so its really a gamble as to which way it would end up going.