The only advice really, is that you have to let your grandson's parent do what he sees fit.
To my mind, too, it's very soon to be bringing someone else into the picture, but we have people on this site who have got together with someone new in less time than that, and gone on to have long, happy years together.
All you can do is continue to be a loving support to your grandchild, because it isn't your choice to make.
As hurtful as it is, your grandson might thrive with a new female in his life, if it works out, and his dad has at least taken some time to get to know this person before introducing them.
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