We finally found a GSD puppy and picked him up yesterday. His name is Dexter, and he's 12 weeks old. Of course, he's just being a puppy, and I keep wondering what I was thinking.

He's actually doing amazingly well to my surprise, he learned down and sit yesterday, cried for about 5 seconds when I put him in his crate last night and slept for 8 hours straight without waking up or having to go potty.
Here's my problem: I lost my beloved lab 2 weeks ago, and it's still tough for me. What I didn't consider is that Lola, my Maltese/Pekingese mix would HATE the new puppy. We introduced them before we picked him up, but as soon as we brought him home, she started going berserk. She's constantly growling at him, toy and food guarding, etc. The poor guy can't even look at her without her growling at him. I'm really confused. When my lab was still around, they used to eat and drink out of the same bowl, sleep together and they were just best buddies. Now she wants to bite my little boys head off. My friend has a fully grown female GSD and her dog is scared of Lola. In a pathetic way.
We initially wanted to wait a little longer before getting a new puppy, since we're still devastated by the loss of our dog. But my little girl just seemed so depressed without him, that we figured the sooner we got a new friend for her the sooner she would recover. Boy, were we wrong. I do not know what to do at this point. I don't want Dexter to be disturbed because she just keeps growling at him. Lola is very attached to me, and now it seems that she's jealous because Dexter is attached to my hip and has been since I met him. What do I do?