T.F.
How did a cheer uniform get black mold? Is it not properly cared for? Are you sure it is black mold?
You don't give us much info as far as the material type. Also, most cheer uniforms are owned by the school so you are responsible if something ruins one.
I'd first let the cheer coaches know what is going on and I would seek professional help from a dry cleaner.
Hopefully you can fix it, if not, you'll have to pay for a new one and the team will not be able to wear that uniform until everyone has their uniform ready to go... in other words.. 1 uniform out of service means the whole team has a uniform out of service unless your daughter sits out.