Not really sure about her2nue

All of this is so bewildering. I thought that I just had a benign lump 3 months ago and I'm now recovering from a mastectomy and reconstruction of my left breast and 2 treatments into the Red Devil. All my hair is gone and my Family and Friends look at me like I'm taking my last breath. My Onccologist is a wonderful guy, but I don't feel like I know what's going on. I've tried to stay away from the internet cause I know how misleading the info can be. A friend who has been mentoring me through this ordeal recommended this site. I'm still not sure what Her2 Nue means. My Doc keep saying the words but I don't know what he's saying. My cancer is small but very aggressive. I had an ocontype test and the results are not too reassuring. My chance of recurrence is very high. Over 26%. Should I have a mastectomy of the other breast? I'm relatively young, 46, which I hear is a bad thing when it comes to breast cancer. And, I have a very young daughter, she is 3. I went to China 2 years ago to adopt her and now I'm thinking.... Did I do her a disservice? Is she going to lose her Mommy, like she lost her first one? Anyway, sorry for being so morbid, just a little scared.