Well, I mean, ok, if you think we won't insta fail on gym 2 simply due to mechanics, I am down to try.
Mary absolutely can pass gym 2 with two Pokemon, even without necessitating max rolls every round. It's not
guaranteed, but she can. The second Gym is usually a reasonable step up from the first Gym, but it's still just 'a step up', not a sudden difficulty spike.
Meanwhile, Drilbur's likely to get a pretty substantial power spike in the next couple of weeks; she's not far off of mastering the Hone Claws/Slash combo, which is an automatic boost to a new and powerful move, and she unlocks Swords Dance at the same time. She'll also rank up several of her Ground-type attacks, although I think it's unlikely she'll get to master any in time, and she'll be pretty close to boosting both Curse and Spark up.
Dreepy's got less of a power spike incoming, but he's still got
a power spike incoming. It'll probably require a bit of a push, but if we can get him up to 3rd badge-level by the time of the next Gym Battle (he's only 2,500 xp off right now, with the xp from a gym battle and the plot finale of this Field Exercise still to come), he'll unlock Night Shade. The same push should also have him master Will-O-Wisp and unlock Curse (which he can use properly thanks to being a Ghost-type), and strengthen Crunch and Fake-Out, both some of his more powerful moves.
That's assuming there's no TM's the thread agrees on getting, there's no additional rewards for anything, we don't get any more free TM's for our work in this town, etc.
As I said; it's not guaranteed that Mary will get the Gym Battle on a 2v3 run, but it's certainly
possible. Drilbur probably won't be at 3rd-badge strength, but Dreepy plausibly could be, meaning Mary's in a disadvantageous position but not a horribly overwhelming one.
And even if she loses-
Well, it won't be amazing for Mary's mental health to lose, but I'm pretty sure Gyms are one of the best places to grind XP in this system, too. They're guaranteed battles against a trainer who's literally designing their team to push you to your limit and teach you valuable lessons. There's no better way for Mary to learn valuable lessons here than to throw herself at Gyms.
And really- if the thread wants to stay anywhere near Nemona, that's what we have to consider. You can't shrug and say you'll wait for a better time where you're more likely to grab the win on your first try. Sometimes, you just have to look at something like a Gym Battle and say, yeah, okay, ready or not I'm going to take my shot at this, and whether I win or lose I'm walking away stronger for it.
Fake edit:
I'm also pretty sure that a solid enough push to Dreepy will have him evolve into Drakloak prior to the Gym Battle. He's at a Bond Level where I'm not overly concerned about him not listening to Mary, so that should be fine; his current issues don't really change whether he's a Dreepy or a Drakloak. That would be a pretty substantial power boost that should make it much more likely for her to win.