Does This Mean, We are Guilty?

I didn't really realize she is mad at me and my husband till on the Halloween activity where my son and I attended; it was trunk or treat at church. The thing is that it was a potluck and I was supposed to bring soup, but because I was busy that day, I decided to bring dessert instead. When we got there, I immediately went to the kitchen to give her the dessert since she was the one in-charged with food preparations. While I was handling her the cookies, I was trying apologize for not bringing the soup instead, but to my surprised, she didn't want to listen to what I was saying, but said "yeah, yeah, yeah yeah" without even smiling, but an upset face! I just left giving her the benefit of the doubt. It started to bother me when hubby told me she has been ignoring his smile and greeting for a while now. Same thing happened every time I gave her a smile! Now, this is something serious I think that needed an answer/attention. I don't know what to do! If we have offended her, why would she tell it to us? I am now thinking of sending her a letter since I am sure she wouldn't answer the phone if I do. I would like to apologize if we have offended her (which I don't remember, since we hardly really talk to each other at church because we are both busy with our callings/responsibilities every Sunday). My question is "are we guilty since it bothers me so much now?" This has gotten worst since she wouldn't say anything or wouldn't even look at us anymore. This shouldn't be happening since we both go to the same church and ignoring is not part of God's teaching. She even more mad at my husband since they are both working at Cub Scout; my husband being a Cub Scout Master and her as a Webelos Den Leader. I am so confuse! She used to be so sweet; and we hug each other every time we see each other at church, or talk at the grocery store. Then, all of a sudden she changed! My husband told me not to worry since we didn't do anything that made her mad at us.