Well buying a lingerie isn't a sin as much as buying a knife would be a sin... It just depends on what she's going to do with it, murdering people would be sinning, and so would buying a lingerie to attract multiple men for selfish reasons... Using the knife to cut meat isn't a sin as God said to kill and eat, so He also made the women for the man and so boosting the attractiveness for her soon to be husband wouldn't be...
This is pretty much what I was thinking too. You put it much better than I,