First, go to llli.org, the la Leche League International website. They have all kinds of help for breastfeeding mothers. You can also contact the local LLL leaders in your area. Just look them up and a volunteer will come straight to your house for free. They're wonderful women and will help figure this out.
Are you sure that's reflux that she's got? I ask because that's what I thought my daughter had. Turned out that oversupply (aka foremilk/hindmilk imbalance) is often mistaken for reflux (or food allergies). A common symptom is a love-hate relationship with the breast.
Does it kind of hurt when you let down?
Do you ever see your milk spraying?
Does your daughter ever cough/choke/sputter at the breast, esp. when or soon after you let down?
Does she have green diapers, possibly foamy?
These are all symptoms of oversupply. If so, she is fussing because either she feels like a hose has been put into her mouth and it is turned on full pressure (very scary for anyone), and she can't handle it, or she is both getting full and still hungry. She's filling up on foremilk and not getting the fattier, more substantial hindmilk because there is so much milk that she needs to eat through all of that but gets full before she reaches the hindmilk.
If this sounds right to you, here's how you fix it:
Feed her on only one side for several hours (say, five) at a time.
It will take about a week to *really* get it back in hand, but you should see some improvement soon. As for the geiser effect, have a burp cloth or whatever on hand to catch it, then put your daughter back on when it has subsided. You can also try other positions, like lying down with her on top of you. This takes advantage of gravity, so that it doesn't choke her - comes out more slowly.
Have heart. We had a miserable two weeks and I was at the end of my rope. But once I figured out what it was - just took a little looking into - it smoothed over and we've been a happy nursing couple ever since (well, now she's teething...eeek...). Stick it out. There are so many benefits. Need I say...*side-lying nursing*??!
And you might even be able to get her off of the zantac!
L.