* * Yes * *. Unmarried women who have slept can be bridesmaids. It turns out that married people can't be bridesmaids, but this topic must not be taken seriously. And now many wedding companies will also provide bridesmaid rental business. People who are professional bridesmaids have to be bridesmaids hundreds of times in their lives, and they are not necessarily unmarried women. As long as you have the will and your sister agrees, of course you can invite her to be a bridesmaid.