It is normal for her to play by herself, especially since it has been only a week. When my son started school (daycare), the teachers told me what to expect and this was a big one. It can take weeks for them to adjust and play with others. I think having her there is a great idea because it isn't for very long. A two year old will definately start socializing, she is not too young. If it is torture on either of you, I wouldn't push it though. My son now loves school and can't wait to go everyday. Now in a couple months I will have to worry about the transition into the 3 year old room!
If she isn't crying a lot, she is actually doing REALLY well. Some kids cry for weeks! It will be normal for her to cry at drop off for a long time, but if she stops after you leave, she is fine! Either way, she will be great because she has a mom who worries about her! You can always wait until she is three and try again if you are more comfortable with that.