You have to get her used to it slowly and very gradually, it takes a long time to get over a fear. Feed her treats around the bath. Every now and then sit in the tub and give her treats, in a happy voice, verbally encourage, but not physically force, her to join you. Put treats down beside you in the tub. Feed her her meals near the tub. Once she's fine with this slowly add water. First just a bit on the bottom, if she's good with that the next day a bit more, and so on until the tub is full.
Do anything you must do to make the tub/water/baths a good thing and pleasent experience. Use anything she likes. You want to associate the bath with good things so she wants a bath to get the good things that come with it. If you force her in, it will scare her even more and she'll be even harder to get in next time!
Also put a non-slip "sticky mat" in the bottom of your tub. Many, many dogs slip on the bottom and get the impression they're slipping and falling under once they slip once, they panic trying to stay standing, as you can understand, this is quite scary for them. Make things easy for yourself and make sure she never slips to bigin with, of this will be another fear to get her over.
Oatmeal shampoo is what most people seem to reccomend. It is really good for their coat. Dog shampoo isn't that expensive, and unless you plan on giving you dog a lot of baths, the bottle will last a long time. (I'm about 1/4 way through a bottle that I've used on Jenny the last three years, plus my previous Beagle who often got into smelly things by following her nose.) But IMO, unless you have a long haired dog you bath a lot, shampoo doesn't matter too much, diet is more likely to affect what condition their coat is in. My girl has a gorgeous coat and I bath her once or twice a year with cheapy shampoo.