How do I stop my chihuahua puppy’s aggressive behavior?

I have a 8 month old Chihuahua, we have had her since 8 weeks. She has always been a lover until recently. She comes to my gift shop with me everyday, so she is around peoples constantly. She has just started barking at everybody that walks in the door. And one day she lets everybody pet her the next she snaps and tries to bite. She has also recently bit my husband twice and my daughter once. What can I do to stop this behavior before it gets to the point where I can’t take her to work and my daughter gets to be afraid of her? Please help!!
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Posted by Cindy