Is she wearing thighhighs, or bike shorts? Since it's greyscale it's hard to tell.

Bike shorts are color-coded black, so it should be thighhighs.
But her knees have too much detail for that, so it should be shorts.
But she is wearing long sleeves and the leave on the bench is a classic autumn thing, so it should be thighhighs...

... yeah, it is hard to tell.

The shape is a bit weird for shorts, but it makes sense for thighhighs. It's common to draw the thighs bulging out a bit since the thighhighs compress the legs and it's a thing some people are into.

The definition in the knees also isn't unreasonable for thighhighs, again because of the aforementioned compression.