Jesus speaks of the widow from Zarephath at Luke 4:25-26 (In fact, he insists there were many widows in Israel at the time). See 1 Kings 17:7-24; Proverbs 19:17.
I cannot help but surmise that the Zarephath widow and the widow in 2 Kings 4:1-7 possibly background (influence/provide a setting for) Luke 21:1-4 and, by extension, Mark 12:41-44. I'm only making a suggestion: it could be wrong. However, I've read similar ideas in commentaries or journal articles that deal with the unnamed Markan/Lukan widow. It certainly would not be a stretch to discern similarities between Kings and Mark/Luke--particularly the example in 1 Kings.