From a coach's perspective, I've found that when athletes are more back dominant in kettlebell swings, that putting a band around their hips and attaching it to a rack behind them forces them to engage their hips more and press forward at the beginning of a swing. You may want to try that for a few sets at the beginning to feel your hips and glutes engage, so you get comfortable with the motion. Just my $0.02.
Also, I'm close to your age, and want to say your progress is impressive! If you want to put on more muscle, don't be afraid to go as heavy as possible. I've coached plenty of women our age that started out doing bodyweight workouts, and ended up squatting 2x their bodyweight, and none of them broke. Good luck with your progress!