Is this ALL that she is doing? Just take a moment and stretch your mind a little more... what about play time running around with neighbors, trips to the grocery store, visiting with Grandma, church, B-day parties, trips to the park, holiday events, laundry mat, going shopping at the mall, etc.
With all of the additional daily and monthly routine activities we can get very busy. I am a hyper chuwawa... kind of person. I can get so busy that I end up avoiding down time at home. It's important for kids to just have down time at home to fiddle around the house playing toys, taking scheduled naps, and just plain 'ol being comfortable in their own home. If I had my way, we'd practically live out of the van. I want to be such a social person that I'd also prefer including socializing with friends, going out to dinner, visiting at their houses, going on trips.
So, I had to learn how to take all things into consideration. I am not so social anymore. After a busy day, the last thing my kids need is to be taken out to a restraunt while the adults yakity yak. They need a home cooked meal, play time in their jammies, a long bed time routine... you get the drift.
Another thing I did to help me prioritize and not overwhelm them is that I give myself a limit on daily activities. Two activities outside of the house a day is the limit. The rest of the day must be at home. Whether the at home time is just playing with mom or dad or playing with bedroom toys, or running around the yard with the neighbor kids, or having Grandma stop buy in the evening with a special dessert... it doesn't matter... what matters is that they are in their own environment.
As far as outside of the house activities goes, I try to balance those with one thing for them and one thing for me. We seem to be able to handle a trip to the gym for swimming and then a quick trip to the grocery store for a corn dog, milk, bread. Another example is that my 4 year old son goes to pre-school 3 times a week so after his 2 hour stint at pre-school, we can go to the park for some play time and peanut butter & jelly sandwhiches before nap. Then, we are home for the rest of the day.
We do something in the morning almost every day of the week. That is largely do to how busy and energetic my kids are. If they don't get out of the house in the morning... naps will probably not happen. I always regret that.
Just one more comment. I have even broken it down to small activities like going for a bike ride (they sit in the ride-a-long attachment and love it) -that's an out of the house activity that I can also hook up with a trip the park for a picnick lunch. But, that's it... that's the only activity we do outside of the house that day. I try to keep it calm the rest of the time.
And one more tip: Try to keep at least one day a week a home day... all day with no errands, or activities. For us, it's usually Monday or Friday (sometimes both). Dad is home on the weekends so Sat & Sun morning are spent at home. If it's sunny we usually do something with him in the afternoon. So, those days are pretty mellow also.
If your daughter is only doing what you have listed, pre-school in the morning 2 days a week, and 3 lessons in the evening or afternoon, I don't think that you are overloading her at all. But, if she's out and about the rest of the time... with trips to the mall, visiting grandma, grocery store, post office, park, visiting neighbors, church, family dinners, etc.... -that's the part I'd be looking at as far as cutting activities out.