It's not hers, either. They both have the advantage of the suit which, let's be frank, did most of the hard work for them on missions. They've had basic training of course and she knows a few more tricks geared more towards shrugging off and escaping a mugger (or worse). But she isn't actually trying to hurt Tony the way said tricks would demand, so those options are all discarded.

She knows her only chance is to use his larger body mass and momentum against him in a situation like this, but she has no time to sidestep his charge before he grabs her by the middle. Her decision is instinctive; she buckles her knees as she curls an arm around his neck and lets herself fall back, twisting her body and bringing a knee up to dig into his side in effort to take him with her and tackle him to the ground.

She has no illusions that this is graceful or by-the-book; Natasha and Clint would probably shake their heads in despair.