Does it feel like she's latching on correctly? Is she starting to drink when she pulls off?
There could be a variety of reasons she's pulling off. It could be an overactive letdown, so she pulls off because it's just too much milk right off the bat. If that's the case, pumping for a couple minutes before you nurse will fix that.
If she's not latched properly, she could be pulling off because she's not getting anything.
Does she seem to be in pain? It could possibly be thrush. Is there patches of white on her tongue or inside her cheeks?
Lastly, it is rare, but some babies are "tongue tied". If you look under your tongue, there is a bit of skin that kind of anchors your tongue to the bottom of your mouth. Sometimes there's too much of that, and it makes latching very, very difficult for a newborn. It's quickly fixed at the pediatrician's office.
Most hospitals offer free lactation consultation services, and a lactation consultant could help you figure out which of those issues it could be, if nothing is immediately sticking out for you.
If it were me, and I was too shy to call right off, I'd look at the overactive letdown first and work from there.
best of luck to you. I breastfed all of my kids, and it was honestly one of the most rewarding parts of parenthood so far.