I'd like to rephrase what 25 essentially said in these short words:
When you meet with a new friend that you enjoy being around and want to get to know him/her more (her...as in platonic friend), do you enter "friendship" talks with them or ask for a talk with them? No? Why not? Too weird. Precisely. Do you sit on the sofa waiting for the phone call from said friend? No you didn't. You just simply got on with your life with GAL, work, family, etc. Those friendships unfold naturally and organically. Nothing's forced, right?
Then you're going have to approach/treat W like a new friend you just met..say...last two weeks.