Do I have to buy her a Corsage for prom?

It's tradition to get the girl a corsage. You may be only going as friends but, you want her prom to be everything she dreamed it would, right? (Yes, girls dream about prom from the time they are like 8.) You don't have to go all out, but you kinda have to get her one. Especially if she sprung for the tickets. A good way to find out what color to get would be, "What color is you dress? I don't want to MATCH but I don't want to clash either." This way, she will tell you but won't know exactly what you're doing. 'Cuz, while she should also get you a boutenier, you don't want her to go broke cuz she felt she had to cuz you were when she bought the tickets....am I making sense? Have fun!