Woah, how did this post turn into a pissing war about who has the most playthroughs? Anyways, back on topic. I married her in my second playthrough of the game. Although she definitely loves MU, I'm pretty sure she still hasn't let go of her feelings for Chrom, as evidenced in Severa's paralogue, where it is implied that she still liked (don't know about loved) Chrom in the future.
Edit: In other words, dat bitch ain't completely faithful.