Hmm... This is actually a good question. The first group is mainly for those who are pretty much very skilled in terms of weapons and martial arts, including super strength, speed, and other physical skills. Flying, for instance, could go into the first group so long as they also don't blast magic or summon minions (so that is to say, the ability to fly would just count as a movement skill). The second group is for those who can do everything and anything.

I think for Looma, she could fall into either, so the better question is—is it possible for someone who can only wield a weapon be able to defeat her in some capacity? OR is her strength and defense so strong that only those who are using enhanced abilities such as magic or other equipment would have a fairer battle?

Keep in mind that a lot of the characters in the game are considered "strong," and even those without magic could have strength or skill to take down large groups of people single-handedly because they're "that good" (quotes because well—anime/manga/movie exaggeration of skills and such). The group composition may also vary depending on who enters where. For instance, if we had a lot "brute force" characters in the first group, then it might not be so strange for Looma to be there.

But if I were you and I had to choose, I would think about her abilities, mentally imagine her going against a few people on our Taken roster, and see how much of a difference in combat skill there is. If you find that she would easily cream a master swordsman despite their own tactical skills and strength, then I'd stick her in the second group. If you think that despite her strength/defense she would still find challenge and could reasonably be defeated with enough skill, then first group might still be doable.