Pre -school or not to Pre-school?...That is the question.

So, this picture really describes who Sadie is to us. She is extremely silly, lots of fun, very dramatic and always singing, dancing and just being a hoot! Which is what makes this next decision so hard. See, Sadie started 2 day a week preschool this past September. Although Natalie did not go to preschool until she was 4, we had thought that Sadie would really enjoy preschool, so we signed her up. It is at the Y and meets 2 days a week for 2 1/2 hrs. My parents take her to and from school and in the ideal world... all would be good. But, here's the thing - Sadie does not like school. She was very excited about the idea of going last September, but once it actually arrived, she has not been much of a fan. Now, she doesn't throw fits and yell and scream, but she will openly tell us that she does not like it and would rather not go. Occasionally, she has given my mom a hard time about going, but they are usually able to work through it. Although there were tears in the beginning of school, the teacher tells me she no longer cries at school and doesn't ask for her mom or when it is time to go home, but she also told me that she spends most of the day in the shadow of the teacher's assistant and that she rarely ever smiles!
The class and teachers are the same that Natalie had back when she was 4 and I really like them all, but this class is just BIG - 21 kids and from what I hear, they are a very busy and very demanding bunch of kids. I hear from Sadie that there are a couple kids that do some naughty things end up getting in trouble and I think it is just too much for her. Even in the best of days, Sadie does not like loud noise and I think the environment of this class just doesn't match her. When we signed her up for this class, it was not because she needed it, but because we thought that she would enjoy it - something that was just for her. With that being said, she doesn't like it and is overwhelmed by it all, so is it fair for her to continue? However, can or should school ever be an option? So... what do I do?
Outside of setting a precedence, I can't think of a reason to keep her in preschool for the rest of the school year. Is that enough? Rather than just pulling her out, we are thinking of having a clear cut end for her. Like a planned ending - maybe at the months end or at February break?
Next year, Sadie will be going to full time preschool and rather than it being at the Y or at a center, it is going to be in someone's home with only 5 other children. For her... this will be better. Who's to say what the transition to Kindergarten will be like.

Why is parenting so difficult? Are there really "right" answers or do we just have to go with the ones that feel right, even if they don't make complete sense?