I'd like my partner to get a 2nd girlfriend

Hey there. I have told my partner its alright and I'm fine with it as long as I know about it and they know about me and we are all cool with the situation.

He has liked somebody for a while and she used to like him back but suddenly went off him; I'm not sure why. I wonder if it is because she knows me and him are together and doesn't want to cause trouble or if it is genuinely she isn't into him anymore in that way. They are friends though and talk regularly now.

Should I talk to her and let her know the situation ? She is an acquaintance of mine but sometimes we are in the same groups in uni. She is super nice and I think would be a good match for my partner tbh but of course only if she is actually interested in him; or maybe they can stay friends.

Thanks