You can also offer liquids in a syringe, like medicine, to get the odd extra ounce or three into her here and there.
Never heard of giving a baby that young Colace. Not prune juice? (Which could also be administered in a syringe)
Along the lines of a smoothie, I had a friend whose DD learned to drink things other than milk by mixing some veggie juice (I think they started with carrot b/c it's a bit on the sweet side) with the milk. Oooh, prune juice and milk/formula together!
Also, by 9 months some babies are taking yogurt, which might also make a nice smoothie. (The culturing of the yogurt partially digests the milk sugar and protein so it's easier for most people to digest than milk or cheese - you'd just add plain unsweetened yogurt to some milk and shake it up to combine!)
You could also try mixing formula or milk with solids - oh, just saw Mimi beat me to that one!
Both mine had EBM and formula mixed with cereal from time to time, but you could just as easily add it to applesauce (or prunes LOL)
How is her weight gain? How are her diapers? Is she having enough - or ANY - wet diapers during the day?