Oh my dear do I have experience with this one!! LOL
When my now 9 1/2 year old was just 2, he found sock fuzz in the tub one night. He FREAKED. He thought it was some bug or something that was going to get him. I hate to tell you, but this is not going to pass quickly nor are you going to just be able to keep force bathing her. That isn't going to deal with her fear. It was literally a process for my son and it took a couple of months, but it was not traumatic for either of us and he went on to love baths again.
First, I started just running water in the tub but not closing the drain off so it would fill. My son still wouldn't sit or stand in the tub though so here I was quite pregnant at the time. I'd have to strip down to my underwear and sit on the side of the tub with my feet inside. Then sit him on my lap and wash him.
After a week or so of that, I would start having him stand in the tub at the far end of it, again, still not letting the tub fill up at all. About a week after that, I would let the tub fill just in the lower end of it so literally, there still wasn't any water towards the back where he stood. Through all of this I tried to get him playing to distract him. By the time I was letting that little bit of water in the front of the tub, I would splash or play with his toys at that end. Eventually he did the toddler at the beach thing where he would squat at the edge of the water and start splashing a bit. You have to follow her cue but I think the gradual reintroduction at her pace will help. It definitely helped my son. As I said, eventually I was able to start filling the tub up again and he'd get right in and take his bath but it took time and patience. Trust me, this is just one of many times you are most likely going to have to deal with something like this. ;)
Oh! The other thing I did was make a spray. I got one of those spray bottles at the store and put water and - oh boy...I can't remember what else I used. :-| It was something to make it smell like tea tree oil or lemon or something. Doe she have a scent she really likes? The point is, before each bath I would let my son watch me spray the tub with the no more sock fuzz spray. (Of course I'd have to make sure his toes were clean before he got in too.) But the spray thing is a psychological thing. We later did the same thing when my son had bad dreams and it became bad dream go away spray. You could spray the tub with something and make it no more poo spray. ;)
Good luck. This is something if you are patient about it you are going to be able to look back on with huge pride in yourself later. I'll tell you, it's a great feeling to know that my son was so petrified but through my patience and steps I was able to help him overcome it in a way that worked for him. I hope it works for your daughter.