his heel is directly on her cheek"

Is that why she is smiling?

"merely as over-the-line and stupid"

Yes. I agree with you Bill.

"throwing her done in the first place"

Was there a struggle which caused them to end up on the ground?

"who helped tackle her"

She said she was blocked, not tackled.

"admonishes him to lay off the standing on her"

That is a plus for the other guy so thay are all not "stompers".

"Hard to say what he'd have done otherwise"

Indeed it is hard to say. He might have actually stomped her.