You have it backwards, I think. The grip he had on her arms is easily broken by Dove forcefully whipping her arms up between herself and Hector, which also has the advantage of letting her break his nose. As I read it, however, she eschewed the practical move for the flashy and mostly impossible one of using her arms' momentum (plus some superhuman leg strength) to throw herself into a backflip, kicking him in the face instead, and giving us the ass shot at about 270 degrees through her rotation. And that's not a wobbly stretcher, it's a very stable full-size hospital bed - which suggests the only possible practical reason for her move - to get a heavy object between her and the crazies who just woke her up.