I would pay a lot of attention to the bolder area in the above quote. Your daughter has to get a good amount of playing time to warrant playing up at 18u. If she is going to be sitting half the innings I don't see this being a good move for your daughter. For recruiting purposes I would have to agree with the others that recommend playing a year at 16u.
Yes D1 is not for everyone because of both the time commitment and player talent.
DD did not want to go through the D1 grind. She wanted to be in a family atmosphere where softball wasn't the sole focus every waking moment, so she focused on D2 programs that met her academic needs and were also nationally competitive. Besides, she isn't top D1 talent anyway, so her desires worked out well. Not sure she avoided the grind as much as she wanted to, but she committed to her number one D2 school on her list a few weeks ago.
As far as your DD's choice. Playing time is never guaranteed. Tell her to play 18s and be so good they can't sit her. It will be good practice for college.