You cannot ignore this concern. But you should also not blow it out of proportion. It could be a huge issue, or not at all.

 Consider:

• Are you basing your assessment of his mother on solid evidence, or just a feeling or a one-off comment?
• Are you likely to be living near your in-laws, or in another city? If you are far away, you may be better able to manage the situation.
• Is the guy you are dating aware of your concern? This needs to be discussed openly. And if you can’t bring it up that is not a good sign.
• Does he also think that his mother is manipulative and interfering?
• Has he developed effective strategies to deal with her? Or is he under her control? 

You are not marrying her, you are marrying him. Does he know how to handle his mother, or not? That’s what you need to know.

All the best,
Rabbi Moss