My kid loves bathing but is always hard-presed to stop what she's doing to get IN the bath. She'll whine and delay, but then have a grand time once the bath is underway! One trick that works with her is I challenge her to a strip-off. I'll tell her, in a sing-song voice, that I bet I can get naked before she can! And she'll be in the bathroom like a shot ripping clothing off her body in record speed. Of course I only manage to get one arm out of a sleeve. ;) (My kid seems to be very competitive... I don't know where she got that from at all.) This strat may not work for your kid. I don't know what makes yours tick but you do, so you need to figure out how to work that to your advantage.
Another thing that would make my child very excited to take a bath is having a special bath toy. Something she can play with only while in the bath. My daughter picked out some pool toys from Target, floating egg-shaped weebles-wabbles, but they don't fall down, animal themed creatures. She loves spinning them in the bubbles and pretends they are skydancers, dancing in clouds.
I wish you luck in discovering the trick that will get your girl ready to clean up. Perhaps a special washcloth and towel embroidered with her name? If she's a girly girl, maybe some special sweet smelling after bath lotion that she can only apply after she's clean? I'm sure you'll find the perfect thing to inspire her to clean up. In the end, peer pressure will get her to do it if you can't. Kids are honest to the point of being mean. It'll only take one of her friends to tell her she stinks to motivate her to clean up. ;)