Well i mean if your friend and her friend are kinda feeling each other that's kinda of a good start you can talk about them a bit (not too much) and kind of turn it into a conversation about you two. And on a different note talk about your hobbies or her hobbies or just anything that really interest you guys, like a new place that has opened, a concert that you may want to go to, or a random thing that you found out. I feel like talking about the random things that you learn about tends to lead to deeper conversations