Why is my puppy so aggressive?

Honey- she is NOT being aggressive - she is playing. All puppies play bite. I have a 5 month old shih tzu maltese mix and he is the best dog we ever had but he get the puppy crazies at times and chases our feet. He does not nip near as often as he did a few months ago and he is getting gentler and minding better. You need to learn to manage a puppy- you should correct, gently but firmly- no smacking. Help her learn the work "no." And you should substitute- she wants to play, so toss a toy for her to catch or we have a stuffed toy tied to a short pole we wiggle around for him so he chases that. Tie a rope on a toy and drag it down the hall. The pup wants motion- not just a toy laying there. Please remember ALL puppies want to play bite in the beginning and there is no shortcut way to turn a pup into a grown up. She will act like a puppy for a year. It is not her breed or aggression or wickedness or anything else - she is just being a puppy. She will calm down as she grows and as you work with her. Good luck. I love this mix. Our dog is very smart, very sweet, very playful and I bet your dog will be too if you keep working with her.