Okay, there are 8 O's, 4 C's, and 6 M's.

I once decided not to date a gi-- -eca-se s-e -asn't e-cited to meet m- dog.
I mean, t-is -as -i-e not -anti-g to meet m- mot-e-.

Logan - E(16) + D(6) + C(4) = 42
sammi - S(5) + G(3) + O(8) = 24
Rottie - A(7) + N(6) + M(6) = 26
Bugmom - I(8) = 16
Karen - T(13) = 13

Letters left to choose from:
BCFHJKLMPQRUVWXYZ

The puzzle letters have now been corrected.