Kid Quantum II (Jazmin Cullen) is part of the reboot (or Earth 247) Legion.
She joined the Legion of Superheroes a little later into the series, as her brother James Cullen served in the Legion as the first Kid Quantum (until his death). They are both from the planet Xanthu. Kid Quantum can count projecting “stasis field” and alter time and reality within those fields among her abilities. In time she was voted in to be Leader of the Legion and had a relationship with Cosmic Boy.
This particular version of Kid Quantum is how she appeared in the Legion Lost mini series.
I cannot remember who the model is or where the source picture came from (I didn’t track that information back then).
The background of the image is a very slightly filtered scan from the Legion Lost series