Laura seemed to keep coming back only to the blood sucking fiend aspect which Mattie did not much to discourage, but played with as a rather vampire troll on Laura. I saw her main point being that Laura's ideas of right and wrong were fixed in her time. To a vampire, all of that will pass and change as it has for Mattie and Laura down through the centuries. Carmilla made the same point in a more romanticized way when she was giving her back story to Laura in season one.You have a point. I think Laura has always been trying to sweep Carmilla's past under the rug because she doesn't want to deal with or acknowledge it, and it came back to bite her (the Mattie situation).
Bingo. And I think that's why Laura is so fixated on the idea that Carmilla has "changed" no matter how much Carma keeps denying it.
Because if Carmilla has "changed," then Laura can keep telling herself that Carm's troublesome past doesn't matter anymore.
And the more Mattie keeps rubbing Carmilla's past and true nature in Laura's face, the more Laura keeps pushing the "vampire redeemed by love" scenario she's got running in her head . . ..
On the other hand, one can argue that Mattie is in denial about who Carmilla is and what drives her. She keeps expecting Carm to "grow up" and put aside these endless adolescent crushes, but clearly that's never going to happen . . ..
Carmilla doesn't care about politics and power plays. As Guy put it, she's in love with falling in love. That's what gets her through the centuries.
(I like that she's a philosophy major, btw. Makes sense that an ageless immortal would want to ponder the mysteries of existence.)