Yep!!! We are just NOT a cry it out type of family. And I don't feel that this spoils your kids to respond to them when you can. After all--I didn't have kids for my convenience! Parenthood isn't easy, and being a baby can be just as stressful!!
Anyways, my two suggestions for lowering your nightime nursing sessions (and yes they WORKED for me--and my kid LOVED NURSING):
1) New pajamas!!! Sounds crazy, but it helped. Initially, I wore satin pajamas that buttoned in the front for easy nursing. I have like 5 pairs. My son loved the feel of them. Still does. But in his sleep, when he'd feel them next to his skin, he'd get a desire to nurse. So I kept him in bed with me (because I liked him there!) but I switched fabrics and type of shirt to a less "easy access". Worked well, took away some of the cues that would make him want to nurse. Search out for some of your daughters other nursing cues and swap them out as well. if you really think about it, you can easily identify some things that remind your daughter of nursing. Save those items/songs/clothes/blankies for when you DO want her to nurse.
2) Keep a bottle of water (or--the horror--milk!!) near the bed and give that to her when she searches out boobie. (I work, so my son learned to take a bottle and I'd pump at work.) Sometimes, just the sucking is what they want to get back to sleep. I started with milk, then once he was used to getting a bottle instead of boobie at night, switched to water. Since a bottle just isn't as cool as a boobie (esp a bottle of water), eventually the request tapers off.
One thing to note though: dropping nighttime feedings is going to lower your milk a bit. If you are looking to wean anyway, then that is a good thing (less milk=less requests to nurse), but if you aren't ready yet...
Another thing to note: this is yet another phase. every once in a while, your kid will go though a spell where they don't sleep all the way through the night after doing it like a champ for months. (who doesn't have insomnia once in a while??) It will pass. Unlike what others have been saying, your 13 year old daughter will sleep on her own.
And believe it or not.... my 2 year, 3 month old son sleeps in his own big boy bed now. And I could not believe how easy it was!!! I was so surprised. I switched him to his own bed at about the same age as your girl (after I weaned him from nighttime nursing--the toughest part-- and once he was sleeping through the night again. I don't recommend trying before this) because I was pregnant again and things were getting too crowded (plus I planned to co-sleep with the new one, and knew I would need some transition time to get the firstborn out of the bed!!) As cuddly as co-sleeping is... eventually you will want you own bed back, believe it or not. (toddlers move a LOT in their sleep--and they GROW! FAST!)
Anyways, the way we got him in his own bed (in case you are interested) We bought him his new bed (a twin), put it in his room (I put the mattress right on the floor, no bed frame at first), and covered it with his stuffed animals. He jumped on it, played and generally had a good old time. Then that night, instead of going to bed in my bed, we snuggled up in his. Once he was asleep, I left. Presto--he slept in his own bed! The whole night!! And... SO DID I!!!!! Ah.. the memories (Now I have a 3 month old, too).
Since you can't cuddle them to sleep in a crib, moving them to a big boy/girl bed is probably the easiest way to get a co-sleeper to start sleeping on his own, I think. Note: when trying this for the first week, you MAY want to go ahead and sleep the whole night with her until she is really used to her new bed, because you may not get as lucky as I did on the first try.
You may be wondering about nighttime wandering, or him climbing back into bed with us on his own?? In order to keep him in his bedroom if he woke up, we baby gated his bedroom door and just babyproofed the room really well, then left both his door and ours open so we can easily hear/see him and respond.
Once in a while, He does wake up sometimes in the night. usually he re-settles and goes back to sleep, or plays with a toy then goes back to sleep, but sometimes he does cry for one of us. When that happens, one of us comes in and snuggles with him til he falls back asleep (fairly quickly), then we go back to our own bed. I actually feel that since he knows that we will come in and snuggle him if he needs us--rather than let him cry it out--it makes him feel more confident and secure, and actually helps him sleep BETTER!!