Like you just said. She is 13 weeks. She is still a puppy and is still learning.
She is biting because that is her way of playing.
Next time she bites, say a loud "Ow" to make it seem like her bites are the most painful thing she could ever do to you (even if it already is) Instinctively, she should let go. If she does, praise her and continue playing. This will teach her that even if she thinks its fun to bite, it hurts you.
If she bites and doesn't let go, even if you say "Ow", then stand up and face your back towards her. Until she turns around or seems to loose interest in you, turn around and praise her. This will teach her that if she bites, play time is over.
No hiting is needed to teach your puppy that biting is a big no-no.
If she is chewing on things, it is probably because she is teething.
Get a teething toy. Watch her carefully. If she is chewing on something she isn't supposed to be chewing on, get the toy and push it in her mouth.
If she loses interest on what shew as chewing on first, and chews on what you WANT her to chew on (the toy) giver her lots of praise. This will teach her that you HATE when she chews on things you don't want her to chew on, but you LOVE when she chews on her chew toy.