Spoilers for year 6, chapter 30 and on
My money for the mole is on one of three friends:
I just don't really trust her right now, more a gut feeling than anything to be honest. It could be because they haven't really been doing anything with her. Never really made her a date option so maybe can use her as a fail safe "here's the mole you probably don't like her anyways" type of situation
We still have yet to be really given any information on all of those letter swapping and writing he's been doing since what 2nd year? Him writing an "important" letter is why he was almost late for the portkey into the portrait vault. He kept having memory problems back in 5th year (because he was most likely oblivated by Peter) because he was probably being used for something. Not to mention his 180 personality switch.
I mean, they're making him more and more invested into the plot. I'm just throwing it out there we never know. Plus it'd be a shock if maybe he's been lying the whole time.
If they're gonna run the "friend betraying you" type of route that is of course, because otherwise they're gonna do some shit like Alanza (which is pretty cheap) or like obviously choice of Peter, considering he spent 70% of his time running away from Percy in year 5.
I'm really hoping Alanza is just a red herring because throwing in someone for the sole purpose of "betraying" us ain't gonna cut it. Especially when a lot of us are already sus about her
I know Talbott is a romance option which normally would take him out of the picture buuuuuuuut I'm leaving him on the list because I don't trust Jam City because I definitely wasn't expecting them to straight up kill a kid in front of me
As for Ben, if it is him I don't think it's a case of him doing it willingly let's be honest. If he's been working with "R" and he had his personality change in Year 6 like that, they might have threatened him and/or hurt his family.
If they do adults obviously Bilton, Peter ("look guys that's obviously the mole" "that's a rat MC" *everyone agrees MC is stupid*)
Merula could have potential been a Mole for Rakepick but after her betrayal in the Portrait Vault I doubt she'd be anymore if she was
YOU KNOW JAM CITY WE'RE A NATURAL BORN LEGILIMENS THAT'S A VERY USEFUL SKILL RIGHT ABOUT NOW!