Kerrie, the fact you have to sit with her to go to sleep isn't a big deal IMO. We have to go to bed with Evan for him to sleep also. I think its best to let them move onto the next "big Girl/Boy" stage on there own. Going to bed by them self is a HUGE thing & they shouldn't be pushed into it KWIM. Like toilet training. Its going to take just as long if you leave till they are ready as it will if you push them too early.
Also when Evan first started with Preschool he became very clingy while at home at first. To the point I thought I should take him out for a bit longer. I couldn't go to the toilet with out him screaming at the other side of the door. From Wed to Wed he was by my side for atleast the first 2 months. It seemed to settle down as things settled down at preschool. Just remember when you do start her, don't expect her to be fine stright off. I know your not, but give her a few weeks where you go together & stay with her & leave together. Let her become familar with what goes on while you are still there. get her use to one of the teachers in perticular so she can build a trust with at least 1 that you can leave her with when you do leave her the first time. A good preschool wont have a problem with you being there with her every 2nd day till she is ready to be left. I was taking Evan for weeks & weeks before I left him the first time. Even if its somewhere you can stop in on your way out to places or on your way home for an hour that way she gets to know the place.
I don't know what to suggest with the home issue. I am sure once things become a bit more normal of a house she will hopefully settle down a bit more. But just remember she did have a traumatic few months in her 1st year & she has had you as her main support from day dot. don't push her to hard to make her comforatble with you not being with her. look at what it was like with my hair & Evan. It bugged me to no end but it was easier to let him make the move to the next stage on his own. & now he doesn't need it to go to sleep. She will be a much happier & secure person in the long term if she can make the transition to "Big Girl" on her own as she is ready.