My mother, the one-woman Christmas Blizzard:
We always celebrate Christmas Eve at my Grandparent's house. When my fiance and I got there, Mom was already there and moping on the couch. Everyone's attempts to draw her into conversation were meant with silence or one word answers. Then, at dinner, she refused to eat saying that she's allergic to all of it. (She's not. She's mildly allergic to beans, which were kept completely away from the numerous other dishes that she can eat and has eaten in the past.)
After dinner, we were opening presents. Mom was silent until she opened her presents (we open them from youngest to oldest). She then started throwing tantrums about the Visa gift card she got (despite having given them and using them in the past, she suddenly didn't know what they're for), trying to give the box of chocolates she received from my sister back to my sister, etc. Basically acting like an ungrateful 5 year old.
We finally moved on from her turn, though she kept up the commentary about it while my uncles opened their gifts. When we got to my Grandma, Mom hit her low of the night. Grandma opened a $100.00 giftcard that my brother and sister had worked hard to be able to get her. It's my sister's first Christmas with a full time job and the first Christmas in awhile that my brother has been able to do much due to his finances. Everyone recognized it as a very thoughtful and well meant gift - except Mom who cut into the thank you saying "Yeah, well their dad helps out on it."
That reduced my sister to the bathroom in tears for the next 15 minutes or so. My uncle tried to calm her down, to no avail, and she left in a huff telling us all to keep our stupid gifts.
The next day, she called to accuse my uncle of restraining her (he didn't) and of stealing her gifts. When he hung up on her, she called my other uncle to whine about the gifts and he reminded her that she'd left, telling us to keep them, and had even thrown the treats from my grandmother into his bag. Then she had her friend send me a facebook message (mom doesn't have Facebook) and leave me a note saying that it's our fault as a family that we gave her alcohol when we know she's mentally unstable (she was not given alcohol and did not have access to it during this time.