[RobGW]

MP3 is clearly going along for the ride. He either has you beat already or he has a bunch of outs and is not folding. MP1 probably has a weak hands with little to no outs. Why not flat call and give her a chance to sweeten the pot. If she folds no big deal just bet the turn. If she calls you still bet the turn to keep her sandwiched between you and MP3 and get all her money before she gives it away to someone else.