Firstly, Blast Girl did ask for backup the one time she ran ahead(if Twister really got knocked a huge distance he probably just would've ran away before she could get there). Secondly Twister is still the most threatening person in the room aside from Locust even if he didn't have a kid as a hostage anymore. The mooks were very little threat at this point and with the hostages out of the way the villains are the priority.

If Blast Girl focused on the mooks, since no-one else is doing much of anything the villains would easily be able to escape.

Edit: Thank you.