If ot bothers you talk to your metamor about the gossip you heard. I would not tell your partner and I would question what your true intention are. Honestly if you do go to your partner any type of positive relationship you do have with her will be gone. It really is none of your business and if it were me I would let her her have a heads up people are starting rumors about her. She very well could have had something she said taken out of context not said anything of the sort. Even if she did say it she could just deny.it and you'll just be left looking like a shit starter
done with poly, the end.