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Hi, Welcome to JustAnswer. I'm a licensed veterinarian and I'll be happy to help. You are right on in taking Ruby and the puppy to neutral territory to meet. . .a place that Ruby doesn't feel the need to protect and defend. I'd do this several times weekly and allow the dogs to safely sniff each other while on leashes.
Remember that dogs do prefer to sniff each others' anal area, so don't force nose to nose sniffing unless they choose that.
It's OK to sternly reprimand Ruby (verbally) with a NO when she behaves aggressively, but continue with the meeting at that point and over the weeks. It's also very important to praise Ruby and reward her with a treat when she behaves in a friendly manner.
Since Ruby feels it necessary to protect your wife, I'd recommend that she not be present for these initial meetings and that you be the one walking Ruby on the leash. After Ruby is more accepting of the puppy with you, then I'd try having your wife walk her.
If you remain calm but firm in what is acceptable behavior, praise good behavior, meet the puppy frequently in a neutral spot, and begin with your walking Ruby, in time she will become socialized to and comfortable with the pup. This is a behavior change for Ruby and will take time. Be consistent with these steps and all should work out and be fun and peaceful.
Hope this helps. Please let me know if you have further comments or questions. Dr. Barbara