The answer depends on whether Ms. Bridgitte (is she your wife?) wants your friend to lick her pussy. If she does, then yes — of course your friend should go down on her and lick her pussy until she orgasms.
If you don't know, then you should tell Ms. Bridgitte about your friend's desire and ask her if it would be OK with her if he does that. If she says no, then forget it. If she says yes, then invite your friend over and tell him that.... after suitable preliminaries, which may include kissing Ms. Bridgitte's feet then gradually licking his way up her legs toward her pussy.... he should lick her pussy to orgasm (while you watch).