If it ever flowers we might be able to identify it from the stalk and flower.

The grass grows to about 2 1/2 feet tall, and gets a small dent seed had about 1 1/2 to 2 inches long. I’m not worried about identifying it because I know the neighbor planted it. I need to get it out of my lawn.

You do not have any pictures, but my wife saw this and planted some in our yard.

https://www.springhillnursery.com/product/pink-muhly-grass

We are investing in muhly grass this year. Hope it doesn't spread like that.

I'm guessing it is some type of fountain grass. As long as your neighbor has it you'll have a ongoing problem. The seeds from their grass will be blown into your lawn causing it to regrow (unless the seed heads mysteriously disappear). I agree with the roundup just wait till it starts growing. You can spot spray it to minimize damage to your lawn.

Last fall she cut off seed heads. I pulled it out of my beds twice last summer. It reseeded from the previous year, so hopefully I can get it under control this year. Maybe I’ll work my way up the line with round up in the grass instead of doing it all at once.