I hear what you're saying. As a captain, to hear a player make that remark about practice for "fun" concerns me though. That tells me that every time she comes out to practice, she's not trying to develop as a player and she's completely content to stay in that safe place win or lose. Granted, she wins a fair bit with her style of game in doubles at her level but I would rather have someone who wins less with an attitude of building his/her game for the future than someone who wins consistently but is essentially stuck because they refuse to develop his/her skills.
I recruit players that have the basics and can compete well on their given levels but are willing to take a chance/risk and add a new skill. Overall, it helps us move forward as a team.
I would just be concerned because if she's complaining about not being able to deal with your game, then what happens when she meets someone like that in a real match.
The problem with having the position of trying to be the team where you expect everyone to improve is that most of these teams also try to assign matches fairly to everyone as well.
So you get stuck putting players in a situation where they may not do well and someone else that you sat out would of done better. (which isnt "fair" because maybe the person you sat out has been working a lot harder then someone else)
That's why my team is not like that. I try to give everyone a "reasonable" amount of matches, but if someone is truely better and has improved they get to play more, that's the bottom line.
Im not a tennis pro either, we dont do drills in practice, or teach lessons, if players want to improve (and thus get more playing time) they need to do that on their own, not look to their USTA League team for that.
We just play matches at practice and that's just for extra match experience more then anything. The expectation is that you should play that match just like it was for real.
Im concerned more with attitude then anything (attitude in getting thru a match).
If you have some pusher on your team who's winning, chances are it's completely out of your control whether they will change, they usually play like that for a reason (usually underdeveloped poor technique or just a general mentality).
Use them where they think they will win, and if they want to stay at 3.0 and keep winning, that's their issue.
I wouldnt worry too much about it unless it eventually means you find it hard to place them in matches on your team.
I have a guy at 3.5 like that, he'll beat almost any 3.5 singles player but at doubles he's a huge liability, we have tons of great singles players so it's hard to put him in a match, again though that's my fault for putting him on the team.
I had thoughts of him improving as well but that's totally up to him I cant be in any way responsible for that.