It took me and my three month old almost eight weeks to truly get the hang of things. It was very exhausting and frustrating, and I think I cried almost every night. I always felt like he wasn't getting enough because he wanted to eat every 1 1/2 to 2 hours. Turns out, he was getting enough at each feeding, but his stomach was just to small to hold much. I really didn't want to use formula, so I fed him that often, even at night. To boost my milk supply (just in case he wasn't getting enough at each feeding)I started feeding from the breast first, then pumping for 15-20 min, even if nothing came out. I was sore for a while. But in a couple days, it got to where I could pump around 3 or 4 oz AFTER he ate, to freeze in case we needed a bottle to go somewhere. And he started going longer between feedings (about four weeks, he finally went to every three or four hours, and one day out of no where at 8 weeks, he just slept through the night, and has ever since. Now, I wouldn't change breastfeeding him for the world. At three months, he sleeps about 10 hours at night, and after his breakfast feeding, I usually pump out around 8 oz to freeze and store for daycare feedings.
I should note, my first child was preemie and unable to breastfeed at first, so I did the pump and feed only, and two things happened. One, he bacame lazy, because with a bottle, the milk just dripped into his mouth and he didn't have to work or suck as hard, and two, my milk supply started tp dwindle some when I went back to work, even if I pumped at regular intervals. The doctor told me it was because when baby actually suckles, it's a different hormone connection, and baby is a more effecient breast emptier than a pump. His neonatologist gave me some sort of medicine (I can't remember the name of it now, the pediatrition should know) that while it was not manufactured to booster milk supply, it did have that side effect with no harm to baby.
One important thing is to make sure your milk is letting down. If it's not, she might get some milk, but not enough to satisfy. I've read that for some women, it takes longer to let down, and that baby could get tired before it happens and give up before filling up.
If you haven't tried it already, WMMC has a lactation consultant (FREE!) that watched how my little man was latching on and suckling, and gave some really good pointer's too.
Last but not least, she may just be using you for the pacifier effect. Pacifiers gag my son because he is breastfed, and he uses his mouth muscles differently that he would if he took a bottle, and he just can't seem to find his thumb. So, at night before bed around 8 ( i promise you'll get there!) he now latches on and just sucks to fall asleep. Some say that letting him do that is bad, and might be hard to break, but I'm getting eight hours of sleep. I know I'm lucky, my first one was nowhere near that easy. I guess you just have to pick your poison.
I hope that helps a little. Good luck. Stick it out if you can (I'm grateful I did,even if it did take 8 weeks!), but remember, sometimes breastfeeding isn't the most important thing. If you are more calm and happy using a bottle and formula, that might be better for you and baby than hating to breastfeed but doing it anyway, because baby will feel your tension.