The only change to Rei's character in the anime that I don't like is that she wants to be a singer (among other things), which feels redundant with Minako. But that's a very minor complaint.
I don't think Minako's dream of being an idol was established until sometime in S, iirc. They sort of phased it out of Rei by that time though.
It's interesting how anime!Rei's character was technically established before the original. Personally I love both versions and think it ended up being a good change for the anime. Having two serious girls in the M trio would've been too much for poor Usagi to handle.
I guess this means anime Rei is the *real* original now.
But seriously, she adds a great dynamic to the team and in her interactions with Usagi. Her subplot with Mamoru in season 1 was kind of great imo.
I know some people don't like the Usagi/Rei/Mamoru love triangle, but Mamoru himself was barely relevant in it. Normally this sort of thing is used to create animosity between female characters, but it was instead used to bring Usagi and Rei closer together.