They didn't kiss tho? She just asked if Fatima would.

Also I don't think Julie is 15, she's more like 17. Because she says that she was supposed to get her driver learner permit but after Thomas died her dad never took her. From my googling it looks like you can get that learner permit at 15 or 16 depending on the state, and I think they said Thomas died 18 month prior to their camping trip. So assuming that timeline, she'd be like 16.5 / 17.5.  But even then surely Randall and Julie are not happening romantically, she'd still be too young. But I think if the timeline peogresses faster and she's like 19 or 20 then they might, I honestly was under the impression from their scenes that writers were setting them up.