The body makes strong associations as far as elimination goes. Once your daughter pooped in the tub, her brain make a link between tub & poop the way you WANT it to make a link between potty & poop. What you might try, in order to break this link and form a better one, is to put a tiny bit of water in the tub to bathe her. If she poops, just take her out quietly and sit her down on the potty - even if she has already finished pooping. Let her sit there for a couple of minutes while you empty the tub and refill it. Then put her back in the tub so that she has a "poop-free" experience in the water - this time make sure there is a more generous amount of water. Simply repeat this process as many times as you need to until her brain has shifted. It could 5 or even 10 such repetitions. The trick is to NOT SAY anything during the process of lifting her out of the tub, sitting her on the potty and putting her back in the tub.  Good luck!