My mom was uncomfortable with my boyfriend who is 4 years older.
Looking back, I now understand that my mom was mostly afraid of me growing up and me dating someone so much older just made her feel like I was growing up way too fast.
Your daughter is going to have to make decisions on her own; ones you don't agree with. I like the inviting him over for dinner idea, get to know him.
The best you can do is talk to her, tell her your concerns, and be there for her if her decisions backfire. Talk with your daughter and set boundaries together.
The more you try and control the more they'll push the boundaries. Get to know him and figure out their feelings for each other.
They're young and gaining experience in the world, learning about how people and relationships work.
Just do what you, be her mother; be there for her, teach her what you know, and be her support.The best thing to do is show you support her but also are just worried.It would also be a good idea to meet him, just to make sure he is a responsible young man.This way, she won't be so afraid to come to you if the need arises.It may not be fun to think about, but she may need some information that you don't want her to have as a parent, but she needs as a young adult.Forbidding it is an act of challenging her to push the envelope on what you will accept.