It's called a "metabolism" and for some people it can be easy mode staying slim until your 20s end and that metabolism starts slowing down.
She's 36 and her weight gain started being noticeable around 2015-2016, which checks out.
Best I've been able to see from the content she's shared, she seems to be doing fine.
Anyway, here's some pro work of hers I had saved, as well.