there is nothing you can do.. go with her and enjoy.. and instead of just watching her get fucked, offer to suck them off until it's their turn. she will love it if you get involved
my ex-girlfriend would make me suck her new boyfriends cock to get him hard so he could fuck her. then i would watch them fuck and lick his cock clean after and eat her used pussy
fuck, that is pathetic...... i'm going to fuck you up the ass in front of your wife and make your little baby dick squirt while it's limp.. then i'm gonna pull it out of your asshole and make your wife suck it 'til i cum all over her face