i breastfed ds1 to sleep until he was 14months old. we both enjoyed it, it was quick, easy and pain/stress-free...so why not? seemed like the easiest/most natural thing in the world to me.
i've been breastfeeding/cuddling/rocking ds2 to sleep everytime too...and will continue it until he doesn't need it anymore too.
just do what feels right hun...i promise you, you won't still be feeding her to sleep when she's 14 years old.