Hi Debbie, welcome to YT!! Your situation sounds alot like mine was a little over a year and half ago. Only I brought a baby Yorkie into my home with my 11 year old Maltese, who has always been a people more than dog person. I would give it time, and be sure to pay extra attention to your Natalie so she doesn't feel left out. New puppys usually require a lot of our attention
It took my Maltese a good 3 months to be "comfortable" with AprilLove, and now they are like sisters. I was worried at first too, because my Maltese would growl at April when she wanted to play and I would wonder if she might hurt her. I was always with them when they were together never leave them unsupervised. In hindsight, I guess I really did rely on how well I know my girl (the Maltese) and I knew she couldn't hurt her, it wasn't in her personality. If you go out, separate your puppy from Natalie. In time, you will know when they have figured out their places in your home. Remember, this is like a big change for your Natalie if she has been your only pup in the house until now. Once she realizes the puppy is there to stay, I am sure it will all work oout for you. Good luck! and keep us posted, would love to see pics of your new pup, I LOVE Maltese too!!!!
PS, I forgot to add, don't try to push their relationship, let them develop it.