I am so pleased we managed to get our bottle lamb's real mother to accept her as hers, even though she doesn't feed her. It means she has a mother and a sister in the flock, she lives in the flock, although she runs to us for milk. I had the advantage of knowing we could not cope with a lamb that thought she was a human, so we planned from the start to prevent that.
You didn't have that knowledge so now there's a problem to sort out. I'm wondering if this could work: go into the field with the lamb, play with her in there, feed her in there and the other lambs will come over to see her, all lambs being so nosey. If she sees you interacting with the lambs and ewes she might start to do so as well. You are her parent, so if you think these sheep things are worth spending time with then maybe she will believe you
If you go in a bit before the lambs' "mad gang whacky races" in the evenings then she may well start to join in with them and make friends. You would need to take her into the flock each day several times a day and at some point she would need to stay in with the flock overnight, not in the house. It would take a lot of your time, but that's what happens with pets. You could take a book or some work and just be there as a reassuring presence while the lamb gets used to her new companions. It's not a very shepherdy thing to do but it could be worth a try do you think [member=215773]GGFrance[/member] ?
With our lamb at bottle time it's interesting to watch the rest of the flock and their reactions. The dam watches carefully and will sometimes still walk across towards us when Lark is feeding, seeming to make sure we do it properly and her daughter is fed. A couple of other ewes will come across to see the bottle and to watch Lark drinking. But the whole flock watches and pauses what they are doing while Lark feeds. So sheep can accept this difference and seem to understand that this is how Lark feeds. They also accept me on my scoot as long as I'm wielding a bottle, whereas the rest of the time I use it for rounding them up! I am sure that after a few weeks of you being in the field with her and them they will understand and accept your lamb into the flock. You might be the one to be upset when your lamb no longer needs you because she has joined the flock as a sheep
I hope there are some ideas in here to help you.