[Qualizium]

Alternatively, (assuming you definitely want to go for the goofy high limit) you could have nine single-squirrel markers and nine 10-squirrel markers. It would mean more markers piled on the card at a time, but it would also make the markers more interchangeable, which means you'd never have to go rooting through your pile for a specific one, you just have a pile of singles and a pile of tens, and you grab them as necessary.

If you want to avoid stacks of markers on the card, you could give her a double track to place beside her card (similar to Dr Manhattan's tracker, but with two adjacent tracks instead of one), and two markers to track her squirrel count like so:

0 1 2 3 4 5 6 7 8 9

10 20 30 40 50 60 70 80 90

I'm more worried whether it feels very squirrel-girl-y (or fun) to have her hanging in the back, not moving, just spending turns building up a big swarm of squirrels. Of course you can throw her into melee before you start gathering markers, but I'm not sure she has the survivability for that to be a very attractive option.