I'm sorry OP she's a bitch and you need to put her in her place

The same thing happened to my moms best friend. She planned her wedding for 2 years, and her ex-husband decided 6 months before the date to have his wedding a week after my moms friend. It really sucked for their daughter because she was the maid of honour for both wedding and had to help plan 2 weddings at once.

If this sort of thing happens with any frequency in regard to this "friend", toward you or any mutual friends, you may want to consider either distancing or even ending the relationship with her. As it stands, it sounds like she scheduled the wedding for that date so that mutual guests would opt to go to just one, and possibly even **** with OP's wedding by causing people to have to scramble to get a second outfit for the wedding or at least get the other one laundered. One event like this is a pretty good indication that maybe you should evaluate whether it's healthy to have someone like her in your life. Ultimately OP's call, especially since there may be details that didn't fit in the post that are pertinent to the situation. But asking someone to move their wedding when they scheduled there's before yours, is a dick move from anyone, no excuses.

Be careful my friend had a wedding a few years back. One bridesmaid was already married but not only fought with some of the other bridesmaids (there was 8) but she started a fight at the wedding. The hotel staff made her and her husband leave then they got mad at the bride and groom. They stopped talking to her that night and cancelled the check they gave for a gift.... my friend regrets including her and having such a big wedding.

Wow it sucks to have friends like that.

Tell her all the stuff is locked in and since she's hasn't started planning it would be easier for her to adjust her date. But make sure you send out your invites first.

I think you should change the date.... to the date before hers.....

If you've been planning for that long, it's likely your wedding vendors and stuff are already booked. If she can't understand that, it's her job to move her wedding. If you've already sent out save the dates and made your wedding day known, people will just have to figure it out if they want to attend both. Your wedding will probably be nicer than hers if she's throwing it together in a short period of time, so there's no competition there.

Say yeah, but move it on her wedding date!

What a wench. Chances are she'll change the date again.