Not the biggest fan of Pokemon debates because there's so much variability in what they can achieve just from the base games with different abilities, movesets, and such, and that's not even touching spin-offs. If they don't have a personality you can base it off of, it's also hard to predict how'd they fight. Wild Pokemon apparently aren't as smart with their move usage as they are when under the control of humans. But I digress.
I'd like to say Mami takes this. In part because her bullets should count as steel type. Bullet punch is a steel type move in the game, and Mami's magic replicates muskets, so they should count as some kind of iron or other metal. This alone should allow them to smash through moves like Ice Shard with ease, given their AP similarities.
Mami's a mid-range fighter who works well with controlling her opponent's movements and working to ensnare them, and given this, she shouldn't fall victim to freeze hax by touching Glaceon, and would have enough time to dodge moves such as Ice Beam or Blizzard, and moves like Ice Fang shouldn't even enter the equation. Mami can also generate many guns/bullets at once, able to keep up with machine gun fire from Homura, whereas Glaceon does not seem to have any strong wide spread move to counter this.
Mirror Coat might be an issue if Mami gets overconfident in the fight, a la Charlotte, but people forget that situation was mostly due to her showing off to Madoka, and that she likely doesn't fight like that on her own. Mami would probably make sure Glaceon is fully restrained before using a Tiro Finale so it wouldn't blow up in her face.
I doubt Glaceon could disable the ribbon trap with their IQ skill, given that PMD traps work like landmines as another user mentioned. Freezing restraints would make them weaker, but mostly likely not enough to shatter it easily, and escape the Tiro Finale.
tl;dr: Mami wins by steel type advantage, and having a better spot control set-up, that would allow her to ensnare Glaceon in a trap, and finish them off with a Tiro Finale.