Telling people I got my wedding dress for free?

I'm engaged to a US Marine and got my wedding dress for free through a program called Brides across America. The dress I got was originally $1800. Well I wasnt telling anyone this...but my mom is. Shes telling people at my church that the dress was free which is really making me mad. She only told a couple people but theyre HUGE gossips so now everybody at the church will know! Is it wrong for me to be upset? I just feel like it wasnt her place to do that (shes bad about this). I didnt want everybody knowing that!