Can 3 females co-exist peacefully

I have 2 Cavs, both are rescues from puppy mills. Grace is 4 and Hayley is about 8. They get along beautifully but Grace continually tries to engage Hayley in play and she has no interest at all. Hayley does have MVD, goes for echocardiagrams bi-annually, but so far is not on any medication.

I have an opportunity to adopt a 9 month old rescue who is presently living in a foster home with 4 other Cavaliers, 2 male and 2 female.

I had been thinking about adding a young dog or older pup and this one sounds perfect, but I hesitate because she is female as are my other two. Both of mine are very gentle and non-agressive. If I had to pick the more dominant of the two it would probably be my older girl, but they are both very sweet and patient with each other and have no problem sharing toys and food.

I know that with some breeds, keeping 2 females can be difficult to do but mine have never had any issues. Am I pressing my luck to add a 3rd female? Would this drastically change the dynamic? Can 3 females co-exist peacefully?

Thanks for your thoughts and advice.

Pat, Grace & Hayley

I may be in the minority here but...

I think that temperament and age are often better predictors of that than gender. My Gracie plays more with other females a room of Cavvies than males... but usually because they are about the same age tend to be about the same temperament... but she also will play with a male if he interested in playing. Brian M here has FOUR girls that get along great. I think the key is to take her to meet the dogs to see how they interact... and do a home trial if you can over a few days. Not always possible, but is a good idea to try.