OG, I could almost write your post to the letter, except for me, my DD was the same as your DD2.
You'll be surprised. My DD had never been away from me when I had DS. She rolled right along with it. SHe took on that big sister roll like a pro. Just as I expect my DS to. He's very much mummy's boy. In fact my DH lives on an Aboriginal community a couple of hundred kms away so the kids are with me 99% of the time. We've moved interstate recently too.
What I saw in DD I'm certain I'll see in DS.
Your relationship will change. That's a given, as are a few teething problems, but she will deal with it in her own way. Allow her to feel what she feels, and allow yourself to feel what you feel.
I made sure I took some time out with just DD too occasionally.