What should I do with my new female Akita?

I live in a warm country. I have a 9 year old Akita that will be outside during the day, but at night come to sleep in my room with air conditioner. Now that I have this new female Akita dog, I want to put them both in my room to sleep at night. It turns my mother cannot think about the f'ing idea. We have a pomeranian that is laid back and a chihuahua (my sister's) that roams around the house. They got along with the female Akita, the male Akita does not like the chihuahua. My sister, who is not responsible with the chihuahua, let him does what he pleases. Nevertheless, my mother is actually asking me to take the dog back because she is afraid of the chihuahua. I told her that instead of giving me a speech, she should give a speech to my sister to take care of her chihuahua. She tells me she will not do it, and that if I want the other Akita I will have to keep them both outside. Outside is hot, and they are breathing through the mouth constantly. I do not know what to do. Should I give the female Akita back so that 9 year old Akita can sleep inside the house with air conditioner? Should I keep them both and leave them outside? Help!