well its up to you. You know her more than we do. Yes your mum once said that you should forgove and marry her because she is a woman but remember,ther are many sides to a coin. Your mother never knew that she would tirn out this bad. Do you think that when you let your mum know about her behaiviour she would let you marry her? No! Never!!
For the age issue,its just a number when it comes to marriage. So many men today are far older than their wive's,and to me its even better that way. There are many decent wive's material out there. Nobody is perfect,but then we must do thing accordingly and respect each other. Cause there is orderliness in creation. All the best!