Considering her daughter is the first in their entire family to get a college degree and on top of that a masters, yes. Why would you be so proud of your kid then not want them to work their tail off getting somewhere with that degree and making a better life for themself
Bottom line is your mil is worried she's going to see her daughter and future grandchildren less. Don't matter nothing about education or whatnot. she's worried about losing her daughter from her everyday life. I cannot fault anyone for feeling that way.