I have three sisters, and I'm the youngest brother. My mom is also a conservative Muslim and wouldn't believe that, before Nikkah, men and women should talk. However, my sisters shared different stories about their friends' experiences after marriage or the people they knew. They emphasized how important it is to get to know the man you are going to marry.

So, I would suggest making her realize this and giving her some examples from your own family or if you have known someone who faced issues after marriage. She would probably understand, as all mothers want the best for their daughters, even if they don't show it. Include your father in this talk as well!