I have something similar with my now 3 year old dd! She knows she's going but is too lazy/won't bother to tell me. I've bought a reward chart and we're using that to encourage her. A friend of mine is using chocolate buttons, one chocolate button for every wee she does on the potty, although I'd prob say a fav snack food rather than buttons, bit easier to remove them after a while! I used the reward chart with my ds1, when he got to 20 (which took a couple of days!) he got a treat of his choice, either a day out or a small toy like a car etc. Maybe when she gets to 50 a DVD. Also have you tried a special book while she's on the potty, one of her fav characters books that's just for potty time.
Another idea is (if you have a downstairs cloakroom) is use food dye in the loo
When they wee it turns a different colour - blue turns green! Or my sister used to use glitter, makes it pretty for a girl. Anything to make it fun, and make them want to do it.
Hope something there helps. Good luck, must be so hard with a newborn too. At least she's eager not to have a nappy on, my dd is eager to not take it off