I have a 12 week old pitbull, and she's already showing signs of a heat cycle...?

So, i woke up this morning and realized there was blood on my t-shirt... I did my research and my puppy is pretty much in heat... She bleeds, mounts, and also the neighbor's dog is always around the house.... Also her "snatch" is swollen... Isn't she a little bit to young? And what should i do??