Hi! I'm not sure how old your Jenny is, nor can I tell if she is smaller than the fawn dog, being part whippet.

The one time I had 2 dogs, my Princess was about 13 and had suffered a series of strokes, and I took in my grandpa's dog, Samantha, after he died. Sam was about 11, no health issues. Princess had been the one and only all her life, we got her when she was 5 months old. Princess sat out in the porch and sulked for 3 weeks, and refused to come in the house! It took some work to get her to come around. Eventually they got along. Sam was always more active, and they had to be walked separately. Princess was not well and moved slowly, Sam was all over checking out everything and dashing here and there. It was OK when we were home, took a little more thought if we went out to a field or the beach or on vacation. (They both lived to be 16.) They never fought over food or anything, but that may have been because Princess couldn't fight at that point. The vet said Princess recovered better and lived longer having the second dog around.

I would also mention that Boo boo is going to need time learning to be a pet, learning about family life. It's always great to already have a dog present, for the rescue to copy and imitate. She looks lovely, I hope you decide to adopt her. I bet you will find more "work" in helping her adapt, than you will in getting them to get along. I just can't tell if Boo boo can walk at Jenny's pace or if it will be too slow for her. But you can work around that!