Starry Eye and Red Topaz have known each other forever.
Red Topaz is the youngest son of Big McIntosh and cousin to Orange Sunstar, who was best friends with ever-lasting "Blank Flank" Starry Eye. So naturally, they spent a good chunk of their formative years hanging out and playing with the same friends.

Starry Eye always saw Red Topaz as an aloof big brother (even when she found out he was assigned and raised as a girl). As a rather tomboyish girl, she felt that they had a lot in common either way. In return, Red found Starry Eyes pretty cool (for a girl) and recognized he could calm down a lot better when she was around.

However, destiny would come to thrust a wedge between them, when Red got his cutie mark and Starry Eyes would continue to have none. Starry Eye fears of being left behind made her distance herself from friends and family, and eventually drove her to a mental breakdown.

Starry Eye would eventually move into a monastery to deal with her fears in a spiritual way, while Red Topaz would remain on the farm.
But sometimes, they meet in town, and occasionally, they share a word and even a laugh together, and that gives Starry Eye hope.