No one is telling OP to "adjust her feelings." Of course they're her feelings. She has shared she is feeling anxious and wants some feedback as to whether she should push through those feelings and allow her daughter to make the visit. What folks are prompting her to do is work through them, not ignore or dismiss them.
I will feel sad when my son graduates high school in a few years. I will miss him when he goes to college. That doesn't mean I should stand in the way of that and keep him home. I'll have to work through those feelings. Same for OP.
This is different. It's very different. An adult is starting a life of their own - sure, no other adult should "keep him home". This visit with Grandma is completely different. It might be too long, Grandma might be too crazy, whatever. The only basis for Op's decision is her interpretation - not ours, not anyone else's - no reason for her to "push through" based on the interpretation of strangers.