At 9 month old this is a way of communicating,its a frustration ,once she starts to talk it will stop most times.all babies use their mouths to express themselves.All you can do in my opinion is move away from her, put her down, if she gets no reaction from doing it it may discourage her .,when she gets a reaction, that's what she wants .good luck
It could also be from teething. Their teeth can be bugging them before they actually show and my son often did this at this age as well. Try giving her teething rings or even wet washclothes. When she bites you tell her no and remove your hand, then give her something it is ok to bite on. Good luck to you.
Margy and Agdal, this is belated but thank you for your advice. Both of yours did help, and it did seem like she would bite the most when she was fussy and tired. Thankfully that habit has stopped, especially now since her top teeth has started to come in, that would've really hurt!
That's good news most children seem to go through a biting stage ,onto the next little habit ...lol