
That was VERY tacky. You don't just invite yourself to be a bridesmaid. If anyone had tried that when I was getting married, not only would I have said no, their invitation might have been, er, "lost"
Perhaps the bride could put her in a truly hideous dress? "I've decided to have each of my bridesmaids wear a different color dress in xyz style. The options are burgundy, navy blue, hunter green, and bright orange with purple polka dots. I'm afraid the first three are already spoken for, but you'll look just
great in orange! Especially with this coordinating yellow butt bow!"
(I know... I'm mean

)
Seriously... don't worry about it. Be honored that the bride chose you.