What seemed like a luxury isn't so much of one now, is it? LOL. The good thing is that you realize you have created this situation, out of obviously good motives -- you wanted her to feel secure and loved. The problem is now, she cannot soothe herself and she wants to feel secure all the time. She doesn't realize that she can make herself feel secure. You also have realized that you have a hard time saying "no" and "she walks all over" you - you've got to change that now! It will only get harder and harder when she's in school, has peer pressure to do things you don't want her to do, and (oh boy) when she is a teenager. You don't need to be best friends with your child - in fact, it's a bad idea. You need to be the parent, and that sometimes (often) means being unpopular with her!
It's best for her if she can bond with other people too - your family members, for example. It will make her feel MORE secure to know that there are so many others who love her and can care for her, meet her needs, etc.
Everyone wakes up during the night - the trick is to not wake up all the way and to put one's self back to sleep. Your daughter is old enough to do this. Do not lie down with her anymore, at least not until she falls asleep. Have a definite bedtime routine - bath, brush teeth, read a story, talk about the day, whatever. But do the same thing every night, and not with any TV or video games for the last half hour - just restful activities. You can use a nightlight or a white noise machine or a CD of soft music, whatever she wants. But make it routine. Then make a rule that she cannot start screaming or crying, she's a big girl, etc. Maybe there's a song she can sing? I used to sing "Good night ladies" but substitute my son's name, and then make up verses about what he did during the day, and end with "Sweet dreams David, sweet dreams David...." Do not let her into your bed - you both need your sleep. Pick her up and put her in her room with a soothing voice but without getting in her bed.
Have a sticker chart or anything that helps her earn what she wants - perhaps a toy at the end of the week, or a trip for ice cream, or whatever. Gradually stretch out the reward period, shorter times at first for smaller rewards, longer times for bigger things. Have her spend the night at someone else's house, have someone else put her to bed.
Whatever you do, BE CONSISTENT so that she knows you mean what you say. You are a single mom so all of the responsibility falls on you, and sometimes that seems like a raw deal. But you also are the only one who can give her the skills she needs to be able to separate from you during the day and at night. Resist the urge to be her friend. You aren't. You are her authority figure and the only one who can really do what is right for her.
Yes, she loves you, but she is also manipulating you. That's not a skill you want her to perfect!