Hey there,
Mi cis-GF has that reeeaaally wide chest going on, and I think she's damn sexy. She's so insecure about it, and I can spend any amount of time telling her how sexy and nice it is. Also, I used to have a very wide ribcage, like a wide male model, and now it's looking more along the lines of a sporty, strong girl. I've seen a lot of bigger girls (though am 5'9 and not so lean), and wider girls, specially in the sports world. I've also had positive attention in that regard from other people, male or female.
In short I think you'll look way better than you think.