J.P.
I have a 9 month old and 3 year old and had the same issues. My advice is to transition her now. I am totally for co-sleeping and my littlest co-slept with me until 7 1/2 months because the night wakings/nursing got to be so frequent. Sadly he is still this way even though we moved him to the crib. I believe I should have transitioned him earlier than 7 months. Since he is sharing a room with his older brother any type of sleep training can't happen and he is still waking up atleast 3x per night to nurse. Of course this could be his personality and maybe not related to the co-sleeping but my oldest co-slept for about 4 months and transitioned beautifully. Also my two boys share a room and it goes just fine, easier than I expected. My oldest never wakes when the little one cries at night.