I'm not going to get into a debate with you over spanking for two reasons. One, like abortion and healthcare, spanking is one of those debates that turns everyone into poop-slinging morons. Two, in this case, it isn't necessary. How do I know it's unnecessary? Easy. From Tiggerhorn's original post:
"It's so frustrating and she doesn't act out in school, at camp, at activities, she's a really well-behaved child for everyone else."
The kid behaves for her teachers, camp counselors, and friends' parents and none of those people are allowed to spank her. If they can all get the kid to behave without resorting to physical punishments, then so can Mom. The reason that the kid attacks Mom and none of the other people is that, at five-years old, she's smart enough to realize that Mom is the only one who puts up with her bullshit.
Mom should have put a stop to this behavior back when the kid was two, but Mom didn't want to put in the work/believed her precious angel would be scarred forever by the word "NO"/whatever bullshit reason Mom came up with for not parenting her child, and now she has to deal with a holy terror.
The kid knows she can't hit or bite her teacher and I guarantee that the teacher never had to resorting to biting the kid to get her to behave. (Seriously, BITING as a form of punishment? What the hell is the matter with you?) Mom needs to talk to her daughter's teacher about appropriate punishments for a five-year old (a.k.a. NOT BITING), find where ever she left her backbone, and then stand up to her own kid.
But Mom will probably resort to doping the kid up because that's a lot easier than actual parenting.