It's not really "very rarely" that she uses it she just knows when to use and when not to, and I understand not being able to watch her do it 24/7 but at the start she did do it a lot.
She's probably smart enough to realize not to do it now that she is almost #1 and also she knows we all know, she doesn't even deny that she moves faster in general with or without the Foo Lion mount.
Carly did the same thing and she got caught tho so just give it time she'll slip up