I have twin girls that are 3 1/2 now. They were born 9 wks. early and I was a stay-at-home-mom, so they never went anywhere and I was very protective of them, also. When they were 18-months old, my ex and I separated and I decided to go back to school. Day care was awful at first, and they were sick so much that I quit my job so I wouldn't have to have them in day care. It may have been just they still had immature immune systems, but I think more than anything that they were just traumatized by our situation (as was I). Several months later I had to get them back in daycare so that I could go to school full-time. They were a little bit sick at first, but now, a year later, they are hardly ever sick. They actually like going to "school" now (so they can go to school, like me!) and do fine.
It might take your daughter a little while to get used to things. Give her vitamins, and maybe supplement with DHA and Vitamin C during cold season. Give her as much extra love and attention as you can. It might be hard on both of you at first, but if this is your only choice, like it was with me, then it will be worth it.
When clinicals start, mine will be in daycare for at least 8 hours a day, and maybe more during the rest of the week. It is hard, but it's better than the alternative, which is me having to work at least two crummy jobs just to make it, and then they're STILL in daycare all the time. Good luck. I really wish the best for you and your little girl