Can a quit claim deed filed after death and property was subdivided before death still be valid?

My brother gave a quit claim deed for 60 acres to a girl friend at the time for financial reasons he was going through for a few years. They later broke up and it has been 13 years since the deed was notarized. He has lived on the place and paid the taxes. He also took out a mortgage against it along with having it surveyed into smaller acreages. He separated out 5.6 acres to give to one daughter. Does these actions show enough that in a court of law that the old girl friend was not the one intended to get the land? She filed the quit claim deed a few days after his death. They were no longer involved and she had even married after their breakup. We think he either forgot about it or she wouldn't sign it back over. The land is in the state of Montana