So to get the 2nd heart for Leah, you have to talk to her inside or outside of the general store. Which I’ve waited outside of for days. She comes into the main town around 1:00 PM on Tuesday, Wednesday, and Thursday. However she goes straight to the pub/bar. Anyone know when she does go to the General Store? I’m currently on: Wed. 10, Winter, Year 1
Leah goes to the general store on Mondays if it isn't raining. However, this won't help you.
I don't know where you got the idea that you can only gain hearts in certain locations but it is not the case. You can increase friendship wherever that character is, by conversation and gifts.
Leah likes most foraged plants so for finding gifts for her is easy. Her birthday is on 23 winter- getting her a liked or loved gift then should be enough for a heart by itself.