My wife doesn't want me to pay for my son's college
I am new here and in great need of help.
My wife and I have been married for 4 years, we were both widowers before we met, I have a 17 year old son and she has two girls, 13 and 16 years old. The way we handle money has always been a problem in our household. My late wife and I lived within our means and agreed that the most important thing was to pay off our debt and save for a stable future. My current wife and her late husband didn't think the same way, they bought a house and went on trips they could not pay for, as a result they had a lot of debt. When my wife and I were married, her financial situation was chaotic, the house was up for foreclose auction and she was many years behind on her student loan payments. Since we got married we went over my wife's debt as a team, there are no more debts left from her old house and we renegotiated the student debt as a couple. Right now I'm the only one saving for retirement, but in a few years we won't have any debt left as my own house is paid off, so things look great.
Not everything is flowers though, there have been signs of resentment in the past, my son studied all his life at a great school but there was not enough money to send my stepdaughters there too, it was a hardship for our marriage but we managed, until now. When we got married, my wife and I mingled all of our assets, except for an account in which there is a substantial amount saved by me and my late wife for the first 10 years of my son's life, that money is supposed to pay for my son's college. But now my wife tells me that she is not comfortable with me spending all that money on his college, when she is still paying for her debt after all these years. She says he should earn his own way in life, that it would teach him a valuable lesson in life, except that I think it has more to do with the fact that she had to pay and that her girls are going to have to pay too. We had a big fight about it and for the first time we can't seem to reconcile.
Any advice on how to handle this situation without hurting my marriage would be greatly appreciated.