Shoogs, I know what you're going through. My DS2 started 3 mornings a week last week. He is 2 and a half, and actually quite sociable and outgoing, and he knew the preschool teachers and nursery from taking DS1 every day last year(DS1 started school last week so it's been a v stressful time for me, although school going fine!). Things are not going as I'd hoped with DS2 - today he was crying all the way there in the car, all the way down the road and tried to stop me taking his coat off, I had to prise him off me to hand him over to the staff, and the pleading, distraught look on his face as I left him was horrible!
I hung around in the foyer and a few mins later he'd stopped crying so I went home. When I picked him up he was fine too (although anxious to go home!). Tonight he has been very distressed at bedtime and called for me for ages (for reassurance that I'm there i suppose)
I totally trust the nursery as I know it, and also know he is fine a little while after I leave, but leaving him there like that breaks my heart. I have a knot in my stomach the whole morning waiting to pick him up. I really feel for you. I am going to persevere as I think he will be fine in the end.
My DS1 went to the same place and he only took 5 sessions to settle but was a bit older, so maybe it's an age thing?
Just to say, though, DS1 had started going to a different preschool which was almost a totally free-play type of environment where the kids just wandered round choosing what to play with. It was all just laid out in one big room, and he just didn't ever seem happy in that type of environment. He was just a bit lost there I think. He is the type of boy who likes to more or less be told what he'll be doing next etc. After weeks of not settling properly there, I took him out, waited a few weeks, then enrolled him in the nursery that DS2 is going to now, where the sessions seem a bit more structured, they do different activities on different days, and it seemed to suit his personality much better. He settled in quite quickly there and really grew in confidence.
You don't say what type of preschool environment it is, but just thought I'd say, yes - give it some time, but it MIGHT be that a slightly different environment might suit her personality better if she tries and tries and just doesn't settle after weeks of upset. I think your instincts will tell you if it's going ok after a few weeks.
ps. the lovely nursery where both my boys have been is fanastic, but my friend's little girl was actually vomiting when she started there as she was getting so upset. She settled fine in the end and made good friends etc. But she has now been a bit wobbly starting big school. It really must just be in their personality.
I am there all the way, worrying with you, at her next session. You are not alone!