Believe me, this sounds like a lot all written out....but. You're only over-scheduled if someone is losing their mind over it. Like the driver, or the child. If everyone is happy and having fun, it won't hurt. She does need ample "down time" where her brain can rest, grow and sustain itself without outside directions and structured things, so I'm glad you mention she is having plenty of free play.
My oldest daughter is 5 and we now homeschool. She has been in piano lessons for over a year and is about to begin violin lessons. The kids (younger two are 3 and 2) all have a French tutor every Friday. Those are their only regular appointments. My oldest has had some gymnastic classes off an on too, but those are short sessions out here so it's not constant. She's interested in starting martial arts, which I don't think would over book her at this point, so I may enroll her in January. I've started teaching my son(3) piano and reading myself, and he also wants to start Tai Kwon Do.
The homeschool group meetings range from three per week, to one or none some weeks, so it never becomes overwhelming, and you can skip things when necessary. The kindergarten curriculum (we're following The Well Trained Mind which has lots of classic reading and subjects to cover) is doable in a couple hours per day, so we're usually done after lunch, and we skip days where she has lessons or homeschool activities and still get through our material. My kids get all their physical exercise right now at the park and running around freely. I haven't sweated the playdates and stuff, because between the park and our daily errands and some daycare here and there, the kids are all very social and I'm just about at my personal "scheduling limit".
The reason it's good to use caution with over scheduling, is that many things (sports, dance) don't NEED an early start (though it wont' hurt). As the body matures, you can "catch up" with other kids by starting a little closer to pre-teen years and making sure the child is interested and not burned out by then having "Done everything for so long". Conversely things that develop the mathematical side of the brain, like music lessons and foreign language study, do need to be started early to utilize development windows, and then can be dropped later (or not) if child loses interest, they still have the early learning benefits. Also, they're less likely to drop out if they're good at the instrument by then, rather than struggling because they started late.
Anyway, if you can afford it, and she loves all the classes, and you don't mind all the driving, I think she'll have great days with the schedule you have in mind. You're right, at this age, the classes are short and geared for kids. I don't think it would be too much for her at all. And if she burns out on some stuff, you can just scale back.