I went ahead and ate the dinner that they had already decided on making. This relative is relatively unknowledgable about Catholic practice and can be critical of the Church once in a bluemoon. This relative had also just gotten off work, and sometimes they can be a little temperamental. I am very nonconfrontational and timid most of the time, and it is hard for me to talk about my faith. I am virtually by myself out here. And now if I explain this abstaining from meat on Fridays of Lent, I'm afraid they'll throw hypocrisy back in my face ("Well you didn't have a problem eating meat
last Friday!") and/or think that I think I'm too good for their meals or something. Take into consideration that they provide me with room and board, so I am in no position to make demands.
Anyway, I could have eaten a second helping of dinner, which I often do, and I could have eaten some of my favorite icecream, but I didn't. Peanut butter filled chocolate candies with fat chocolate ribbons/swirls in vanilla icecream.

Oh well, I think it's ok. It's the spirit you're supposed to be worried about, not the letter of the law.