Obviously I don’t know what your finances are like, but is it possible she’s just enjoying herself and considers it a hobby? Comparing it to other games, $100/month can seem ridiculous, but comparing it to other hobbies, it might not be that bad.
I used to be unwilling to spend any amount on a mobile game until I thought about how much I used to spend playing Magic: the Gathering. Sometimes hobbies cost money.
That’s true.
With a T9 phone, I used to be able to send a complete text message without ever taking my eyes off the road.
Now that I’ve got a touchscreen I’m swerving all over the place every time I try to text. It’s way less safe.