sirrahved,

What does Angel do when Muffin starts to play with you? Does she act aggresively, or is it a matter of Angel taking toys away from Muffin?
It could be that Angel and Muffin are trying to figure out who's dominant. Unless Angel is attacking Muffin over toys/attention, then probably it will be resolved with time. Maybe for now you should play with each dog seperately, and reserve some time for Muffin to play by herself by restricting Angel to another room.
Good luck!

Pembroke_Corgi