If it's only been 2 days, I wouldn't worry yet. I think you can wait up to 5 days or a week before you need to worry. Unfortuantely, I can't give advice on the water intake as I breastfed and I didn't give water to my son until almost 5 or 6 months and then he didn't like it so didn't drink much at all. Other things you could do, is gently massage your baby's stomach (around the belly button) in a clockwise circular motion a few times a day (not after you feed her though). Also, you could try to apply some vaseline on her butt to (sorry to be so graphic) make it easier for the poo to slide out.