For they all contributed out of their abundance, but she out of her poverty has put in everything she had, all she had to live on.
The story of the widow's gift is often used to promote the concept of sacrificial giving, usually in a big church cause or project. But I believe to apply this passage in that fashion is to get it wrong in the worst possible way! Jesus did not point out the widow's gift to commend it. He is pointing out a spiritual tragedy.
The entire context of Mark 12 has Jesus confronting the Jewish religious authorities. They are seeking a way to put Him to death. They have sent a series of questioners to find fault with Jesus in an attempt to gather material to charge Him with some offense. They fail to do so each time. At the final confrontation in Mark 12, Jesus goes on in His teaching to condemn the scribes for their hypocrisy and selfish spirituality as perpetrators of false religion. They are guilting of receiving in His words "greater condemnation". And what was one of their awful practices deserving a hotter hell? They "devour widow's houses" (Mark 12:40).
Right after Jesus condemned the Jewish leaders for stealing the livelihood of widows, this lone, very sincere widow drops in her two copper coins, illustrating the evil in a religious system that took money from the poorest, who could least afford to give it, but did not care for them in any substantial way. Human religion requires sacrifice, but gives no hope or help. Jesus came to end that evil. And it should never be part of His church. That doesn't mean the poor may not give to serve the Lord. But it does mean that the church that receives such gifts should substantially commit to assisting the poor around us so that we are not guilty of greater condemnation.