Hi, K.!
First of all, let me just say in my opinion, you did nothing "wrong" early on. Laying with your child until they drift off is a totally normal, and acceptable, thing to do. The only time I don't is if my husband is wanting my attention that night, I will kiss the kids and out the door I go. Hubby needs me. But other than that, I am happy to sit with my 4 year old until he goes to sleep or at least gets drowsy. I did the same with our 10 year old when he was younger, and he is just fine. It all depends on the child, and a smaller part the parents' actions.
This is not a 22 year old. This is a 9 year old. Help her feel as safe as you can, and slowly start weaning your way out of the room. Find out what is triggering this, because there are plenty of parents who co-sleep until age 5 who don't have this issue, so again, you didn't "cause" this. Perhaps something has scared her, or maybe she doesn't see you or dad enough during the day for her liking and she is using this to get the attention she needs. Whatever it is, please don't beat yourself up. Yes, it is something that needs addressed, but no, you didn't do anything wrong.
Tips:
1. leave a hall light on for her (this seems to work better than night lights because it makes them feel more connected to the rest of the house/people outside the room)
2. soft music or white noise, this helps my 10 year old tremendously
3. give her control. She takes out any scary items like dolls. She chooses the background noise. She chooses which light is left on. Then, she must try on her own to sleep.
4. if it becomes a serious issue, which it doesn't sound like it is just yet, then seek counseling. There is absolutely nothing wrong with discussing things with an unbiased, neutral third party.
(if it starts affecting your marriage or other aspects, time to up the game plan. I know if my husband starts to feel neglected because I am constantly in the kids' rooms, things are not ok at home!)
Good luck!
PS - and I LOVE three 3princes1princess' answer! She is still a CHILD! Do what you and your husband agree upon. It will all work out! =)