[-1] Beast Change
[-2] Hulking Size and Claws modified by Human Form
[-4] Supernatural Strength
[-1] Nimble (no defense penalty by Hulking Size)
[-1] Supernatural Toughness (catch is poison)
Probably attacks and defends at superb (+5) skill with weapon 6, effective Might +13 for breaking/lifting, +9 for grappling. Armor 2 and ten stress boxes. That's what she could have for max shapeshifting effectiveness - this build allows her to be human-sized human, cat-sized cat, giant-sized human and giant-sized cat, depending on what combination of forms she uses. Not weak, but not really broken either.
Possible weaknesses for the character include the following;
1) Poison (or whatever her catch is). Duh.
2) Social encounters demanding Presence, Rapport and Empathy.
3) Encounters with, say, a White Court vampire. She can go ahead and grapple with him if she wants - that only means autosuccess in his touch attack.
4) Encounters in places where she cannot change (too small room, corridor) or does not want to change (i.e. in the middle of crowded street)
5) Wizards. Wizards can counter anything with enough preparation.