u/AK56SIG716i

So I recently met a girl at my open university, she was with her mum and I was a little bit nervous because of that but still managed to impress her mum and then her. I reached out to her and asked her for her number and we had a good humourous first conversation, we only talked for once since we met. She's older than me. Since it's an open university, we won't be meeting any soon. How do I continue to talk to her. Though I don't want it to be an "online Friendship" cuz I know it's so immature. Thanks for reading, help me with anything you can here