Does this meme really surprise anybody? She's an outgoing tomboy with a gay pride flag for hair. This isn't subtle subtext, like Kirk/Spock slash.
As if that wasn't enough, she has a butch-as-hell girlfriend from school. Here's a fun trick: re-watch Griffon the Brush Off and imagine that Gilda thinks Dash and Pinkie are a couple. It's like a whole new show.
This is all unofficial, of course. None of the ponies have shown any sexual orientation, except Rarity, who's been confirmed as straight. Or at least bi, I guess.
I hope the show never pairs up all the girls with boyfriends. Having an out lesbian on a kid's show is probably too much for Hasbro, but leaving things ambiguous makes the show about 20% cooler.
Rock on, Rainbow Dash.