My daughter in law has issue with praying namaz with concentration, so she ask me to overcome it, can she pray her eyes close? Because in that way she can concentrate

You can pray with your eyes closed. It does not invalidate the prayer. Yes, generally it’s not recommended because in prayer we are standing before Allah and talking to him, and when you talk to someone you have your eyes open. But if closing your eyes helps you concentrate better, then you can do that. It’s completely ok