Use magic to move her closer to the bed.

Blue energy takes hold of Wanda and slowly moves her closer. She's surprised, but doesn't make any effort to stop the magic, although she undoubtedly could, since her power is so much stronger than Billy's.

Billy is dimly aware of the wrongness of this, but can't bring himself to care. He moves Wanda to Sam's side of the bed. Billy untangles himself from Sam, and goes over to Wanda.

Billy undresses his mother. The blue energy is in place, displaying them before Sam, who has grown hard by the time Billy is unbuttoning Wanda's blouse. He slides her pants and underwear off, then moves back up to slowly unclasp her bra.

Once Wanda is fully naked, Billy wonders what to do next.