How important is it to you (and your partner) how well you get along with everyone who is in your "poly network"? I have encountered different networks that have very different expectations - some would rather have a life where everyone can at least tolerate each other on a friendship basis, others have no such preference. I don't feel that there is a wrong or right answer for that - it's up to those involved.
But the answer to that question for you will definitely affect what you should do about it.
If there is a general understanding that everyone will get along, then you need to do two things, in my opinion - voice your concerns to your network at an appropriate time, and also try to get to the bottom of why you don't like this person. Is there a specific reason that you can find? Is it that you are feeling some sort of jealousy from the point of view that you feel that her coming into your life might cause you to feel short-changed about something.
If there isn't this understanding or expectation in place, then you are going to need to find ways to deal with it - sort of coping mechanisms. This might be distancing yourself from her (if you haven't already) but also making it plaint to your loved ones that you really don't want to hear the "gushy" love-talk.
I think that either way you need to make sure you are open with your partners about how you feel, even if you frame them as "unfinished thoughts" for them. Give them what they need to help you and support you.
"Listen, or your tongue will make you deaf." - Native American Proverb