Once Abby has more than six they will be constantly rotated (because she feels that will be the fair thing to do). So the ones she has currently are listed here:
Poochyena - Jethro
Obtained - June 1st
Level - 15
Moves - Tackle, Howl, Sand-Attack, Bite
Houndour - Tony
Obtained - June 3rd
Level - 13
Moves - Leer, Ember, Howl, Smog, Roar
[Updated July 4th, 2011]