I would advise her to tryout for a variety of teams, not just 16U or 18U. Look to try out for the best teams she can make, and then make her decision based on the coaches and other players, and whether she will have opportunities to pitch. I don't think there is necessarily a right or wrong answer, just help her find a situation that works for her and can help her toward her goals.
Does your DD have aspirations of playing college softball? If she does, I would recommend she gets on the best 16U team where she will be the #1 or #2 pitcher. She will not see enough pitching time as a #3 on most teams. Find a team that plans to play showcases and emphasizes getting their players recruited. I would not recommend jumping to 18U. She needs to stay with other girls in her recruiting class.
Biggest thing is to figure out what your DD wants to do. Does she want to keep playing? If so and she is going to be a freshman try out for the local JV/Varsity squad at school. She should also find the best travel team she can be on and still get circle time (probably at a minimum 1/3 of the innings).
If she just wants to have fun and not be serious about softball unfortunately there just are not a lot of rec type opportunities at that age (at least in my experience).
The DD pitches and plays 16U as a 1st year 16. As a pitcher, during tryouts last fall she wasn't ready to pitch 18U; as an outfielder & hitter she was at the 18U (not Gold) level.
When this Spring/Summer season began, she participated in the Pennsbury Showcase with her 16U team. She did her due diligence on schools she was interested in academically and wrote/emailed those coaches.
Since DD is only a rising junior, feed back from the DI's she wrote was minimal as they're not really permitted much contact prior to 9/1. Many of the D III coaches interested in DD wrote indicating either they had seen her at the NFCA Academic Recruiting Camp prior to Pennsbury or stating they saw her pitch/play in the tournament and supplied very honest feedback on which she did well, what needs work or inviting us if we're in the area to tour their campus to ring so they could meet our family.
16U doesn't seem to be any detriment to DD's recruiting to date - then again she's not looking to play at UCLA, Stanford, Alabama, Georgia, etc.
If her 14u season is over and you're in Vegas, then I'm guessing she's playing rec ball, not travel ball. Try to figure out if she still wants to play softball or not. If she does, have her try out for some travel programs. That will help her get ready for high school ball even if that's as far as she wants to take it.
This was a mistake with the HUGE difference in maturity. (DD was an alien in the 18U team - socially. And the things I know she heard that those 18u-ers would talk about,.........YIKES!!!)