Freaked on MIL

I freaked on my MIL this morning. I'm pregnant and hormonal as it is. She was in town and stayed at our house. She decided to lay on the floor with her dog and what did she use as a cushion/blanket? None other than the quilt my great grandmother (who I was VERY close to) made me by hand that was on a display rack. I received it almost 20 years ago and it's never been off of the display rack, right on the floor next to her black lab! (White and pastel quilt). I was so heated and said some mean things to my husband out of anger that she apparently overheard. How do I go about apologizing? It literally broke my heart to see that quilt on the floor w dirt and dog hair. My great grandmother passed 6 years ago. I feel like a bitch and I didn't mean to hurt her feelings.