Help with my 5 month old italian mastiff and her aggression?

I have a 5 month old female italian mastiff that I got from someone who had an accidental litter from their 2 mastiffs. She came from what seemed like a loving home. I took her home and introduced her to my husband and my 8 month old mix breed. She does fine most of the time with my other dog. She has now tried to attack my husband 3 times and my sister-in-law once. She also got in attack mode when I took her to a park to meet some friends. She has never showed any aggression towards me in the 2 months that we have had her. My husband has been nothing but nice to her and is even the one who feeds her twice a day. For the most part she is good with him but the minute he leaves the room and tries to come back in, if I am in that room she gets aggressive towards him. We had trainers in and while they worked with her they tried to go after them twice. I love her and wanted nothing more then a big loving family dog but I am afraid of her and I fear letting anyone in my house seeing that she wont even let my husband near me. I'm even more scared because we plan to start a family soon and I don't know how she would act when I have a baby taking my attention away from her. Any ideas? At this point I don't even like the idea of giving her to another family knowing that she has bit my husband twice (once bruising and once drawing blood).