I don’t think so. From what we know (which isn’t much), she’s just a waitress Dean has a fling with as a demon. Nothing good can come of that. If anything, she’ll end up much worse for the wear once he’s done with her- if she lives at all. It would make absolutely no sense for the story for her to be Dean’s ‘Colette’. I hope to Chuck that none of the writers would be so stupid as to introduce a character in s10 and have her ‘know Dean’s true self and love him unconditionally’ enough to make him stop killing. That would actually literally ruin everything. I have to trust Jeremy Carver. He wants Cas to be Colette. He’s leading the show in that direction. Anyways, they made a big deal with April being Cas’s love interest and again, it turned out just to be a fling. The whole point the show’s been making forever is that Dean’s had no success with a long term love interest thus far because he keeps trying to make it work with people who aren’t ‘in the life’. This always ends with them being in danger because his enemies go after them. The key is finding someone who is already in his world, can fight for themselves, and has seen Dean at his lowest and accepted him for who he is and all he can be.
I don’t know who this Ann Marie will turn out to be but there is no way in Hell she can boast all of that. She’s being introduced way too late in the game.