Based on this video of their trainees (Dec 11, 2021):
and Girl with blond hair without dark roots: 7:32
Bailey dyed her hair blond with pink highlights shortly before vid was released. She was in Korea (normally in America) and interacted with YGX dancers around the same time.
There are pics of her wearing the same black cargo pants as in the second part of the vid.
People have said that she has been training with a vocal coach, but I haven't confirmed this.
Bailey is very successful as a choreographer, and just did Taeyang's Vibe choreo, so I don't know how likely this is. She's only 18, so she might just be trying different things out.
Even if that is her, she might have decided to just focus on choreography/dance over the last year, and is no longer in consideration for the group.
I took another look at this pic because the lights looked familiar. The ceiling is exactly like TBL's dance studio when you increase the brightness (Bailey is facing the other way so that the wood beams are vertical).
The girl with blond hair in the trainee vid is totally her. Way too much evidence to be a coincidence.