So my new degu is a rescue from a family member that had to move and couldn't take him with. He is young, my cousin only had him for a couple months, but the last 2-3 weeks he had hardly been handled. I read nearly everything online about taming them and how you have to take it so slow because of their trust issues. He won't take food from me yet, but it has only been a week. I can get my hand under him though, and even pet him but he is very shy. Also, he was living in a 10 gal aquarium before, and I moved him to my old chinnie's home which is huge, so I image he is still adjusting to that. My mom decided to do her own taming I guess, and I have told her many times to take it slow and how they can hold grudges if miss handled. But she went ahead and has been transporting him from different cage levels, which is fine, but today she decided she needed to take him out, which I didn't think he was ready for. On top of that she brought our dog in with her! Now I do bring our dog in occasionally so that the animals know each other and I can reinforce (under supervision) that the dog only comes in with a person and that Draco is off limits as a toy/food. So she takes him out and he seems okay but frightened and then he goes for her shoulder, which she let him do because our chinnie used to do. He then climbed backwards and looked like he was going to try for the cage. Of course I had to grab him to keep him off the ground and he bit both of us pretty well. I told her she needs to take it slower and not have the dog in the room during handling and she said I am not being aggressive enough and he is never going to tame this way. We've had him one week! I've read online that it can take months to properly tame a degu, and that some never really care to be handled. Am I wrong? Am I not being aggressive enough?
No, you're correct and your mother is wrong. Taking him out and overwhelming him, like what happened, can seriously slow down or even halt the taming process. Degus have excellent memories. I would leave him alone for a few days (besides offering treats and gentle petting if he allows it) to let him cool off and then start trying again, slowly. It's best to let degus come out on their own (so you'd want to do this in a dog-free, degu-proofed area like a bathroom, walk-in closet, small bedroom, etc.) rather than force them out, as it helps build trust

. It can take months to bond to a new degu and some are less social than others.
That being said, a bite won't mean he'll never trust you guys again or anything. I rushed a bit with my first pair of degus because I was used to hamsters, mice, etc. I knew how to read their body language and was used to just scooping them up. I tried that with a new degu and she bit me pretty hard

. I slowed down and she ended up maturing into one of the friendliest degus I have ever had...riding around in my hoodie all day, learning tricks, and roaming my bedroom.
I would also consider getting a second degu (preferably a baby since that's the easiest intro). They really thrive in pairs or groups. Even better, if the second degu is used to people or is a baby (and therefore very curious, ha), it'll speed up the bonding process with your adult

.