It can be a bit upsetting when they do that. Try swaddling her before you feed her, so her arms don't get in the way. Also have a look at baby led attachment. Sometimes you just have to let them go and have their little trash and find it themselves. DD2 used to get so cranky at me for trying to help, she got awful confused when fingers and stuff were in the way cause she just rooted around and tried to attach to anything that moved.