I was always leaning toward these two as opposed to Starlight and Sunburst, but this moment completely sealed this pair in my head.  
They’re evacuating the school, there’s a Grogar-boosted Chrysalis just outside, and Starlight is staying behind to give them time to escape. This could’ve been the last time they saw each other, and they knew it, (they both knew how much Chrysalis hates Starlight) yet in the midst of all this, that final look they shared was just so… pure.
 
I’m a fan of the childhood friend romantic interest trope and Sunburst and Starlight definitely get along well but they did’nt have any moments that hit anywhere near as hard as this one.

now kiss

The love is strong with these two.

Those best ponies are made for each other