I work at a doggie daycare and I just wanted to add to what people were already saying about how she acted while you are around...
We never ever let the owners be in the same room with their dog while another dog is present, especially while we are testing them out. A lot of really really great dogs can be very protective especially when they are in an unfamiliar environment which can cause them to do things they ordinarily wouldn't do... We usually let the owners watch through a window and that is fine with them..
It is so funny because a lot of dogs at daycare will act the total opposite of how they act at home! Owners never believe me when I tell them that "Oh boy, he sure likes to bark a lot"... they think i'm crazy since he never barks at home! Or if I tell them that he played with every dog when at home he is very shy towards other dogs... etc.
I think daycare can be an excellent experience for your dog and for yourself, but you HAVE to find the right place. After you find out how they work then think about whether or not you agree with their procedures. Daycares vary so much from place to place... Were I work, we are outside all day. We do not accept agressive or un-altered pets... If a dog bites another dog or gets in a serious fight then they are automatically kicked out... we have a no tolerence rule. We also allow people to come tour at any time of the day so they can see what it is like at all hours.. We never leave the dogs unattended and there is always 1 person per 10 dogs. We are a smaller daycare, which I really like because we have a huge yard and every dog stays together. On a busy day we have 25 dogs...
Some of this stuff may seem like common sense, but there are some bad daycares out there! I toured one once were the facility just seperated the dogs into pens by "level of agressiveness" so all the agressive dogs were together! this makes no sense to me... they also take like 100 dogs a day... yikes... also I have visited a place where the people leave the premises and just let the dogs stay out back!! Granted, it only cost 5$ a day...
Ok ok... I'm getting carried away.. I just like talking about my job!

! I hope you find the right place for your pup!