Bottom line is this: Is it possible to coach the team and be friends with all the parents at the same time?
ALL the parents? Probably not - that is somewhere between 20 and 30 people so the odds are poor in any situation. Never mind when you have authority over their little cupcake. As a coach you ave to be a benelvolant dictator - so some of your decisons wont go the way everyone wants. You can't please everyone.
Some players will get better or mature faster than others. Some will lose interest. Some will gain interest. Goals of individuals and families change. And so on...
There will be times where some parents don't like your decision - that doesn't mean they can't still be a friend or friendly.
We're 10U, and are told by other coaches we talk to that this does settle down as parents get more familiar with the game.
10U is by far the worse age group for parents. They are untrained & unaware. Everything is new and a HUGE deal. The players do weird things. There is chaos on the field. And so on.
Yes it generally gets better as it the girls get older. The game transitions over to being the 'girls' game versus the parents. The parents and players prioriites change. The kids grow up and learn they can so 'no' to their parents - so there are more players are there because THEY want to be versus the parents. At some point they learn to drive so are not as reliant on the parents to bring them to a practice. Many others just figure it out over time as they start to interact with the older age groups.
Also the majority of the real nut jobs mostly leave the game, run out of teams for their kids to play on, can't get players for the team they created for their kid and so on... Or their kid realizes they can say "No" and put their foot down.