Bridesmaid no more!

Is there someone else that you'd rather have as your one bridesmaid or are you just scrapping the wedding parties altogether? If it's the latter, just tell her that's the case because you want to keep things more low-key this time around and I don't think she'd take that personally. If you plan on replacing her with someone else, I don't think there's anyway you could take away the bridesmaid title without running the risk of seriously damaging your relationship.

Tell her that you and your FH have decided to keep it intimate and not have a bridal party.

Sorry, but I think that would definitely put a huge strain on your relationship if not completely end your friendship. But ultimately, the choice is yours on if having her as your friend is important to you.

Even if you two are close ultimately her main task is to be there the day of. You can have a few bridesmaids if you want but make sure you know who you want in your bridal party but like other PP's said, you kick her out (even if you are just not that close now a days) especially to replace her with someone else that would most likely end your friendship. Either no bridal party or keep her. If she was not a disappointment as a BM in the past I am sure you will not have a problem.

Unless you have already asked her to be your bridesmaid, I don't see why any explanation is needed. You just pick who you want.

If you have asked her already, then that would be pretty rude to tell her never mind, you want someone else.

Agreed with everyone else, but I also have to ask what you mean when you say you're having a pop-up wedding?