I agree that this is fucked up, but the bitch pretty much was asking for it... The only thing she didn't say was "slam my face into the wall" cuz he was fucking asking for it.
Like many others said, if you are placed under arrest... just go with it... resisting the police when you're under arrest is ONLY going to get you fucked, not them.
I guarantee this lady won't get a fucken dime from the police department, because the cop was calming walking her to his car and she was thrashing and trying to resist arrest... so BAM... he slammed her down. He also asked her like 15 times if she was going to calmly walk to the car, and she kept bringing up irrelevant shit about her kids.
In summary, no she shouldn't of been slammed into the wall face first... but I doubt he intended it to happen like it did.... and resisting arrest only gets you injured / in more trouble.