Human Aggression in House ... Guarding Behaviour

My ACD mix has developed a really bad behaviour... house guarding. The only time this is displayed is when people who aren't my husband or I come in the house. She will bark, chase after, jump, and has bitten (actually a nip, but still a bite). Outside of the house she can be wary of some strangers, not all, but she allows people to approach and pet her, and as soon as that happens all her doubt is erased and she becomes a wiggly, jumpy, love happy maniac. She really is a lover of a dog.

But in the house....

I have another dog who I know she picked this up from. Riley is a house guarder too, but he's much more passive about it. He will threaten and bark but never get close enough to bite. Ember is smaller than he is but has much more courage. I'm really worried she actually WILL bite someone hard enough to hurt or draw blood.

Also, I've recently started to have her sleep in the bedroom with everyone else instead of her crate. It's only on the days that she will be crated during the day while we are at work, as I don't think it's fair to crate her during the night and then again during the day. However, the past two nights we've done this she has charged the door growling when my husband comes in the room. The first night I think he woke her up from a deep sleep and she actually almost bit him until she realized who it was. The second night she charged growling but then realized it was him before escalating further. If keeping her crated for bedtime is recommended I will continue to do that... I honestly think she might prefer sleeping in there anyway, though she does do very well sleeping overnight in the room - she stays in one place the whole time.

Can someone please direct me towards some things to do to help train her out of this? What do I need to start with? We JUST finished very basic obedience, fyi, and have a long ways still to go with that. Ember is very independent.