Will letting my baby use a pacifier make it harder for her to nurse?

Nipple Confusion? The short answer, of course, is "maybe." babies have a reflexive need to suck, but the way they need to suck to nurse is different than how they can suck on a bottle or pacifier. In the first week or so of nursing, the different shape of a pacifier may make learning a good latch at the breast harder, but many babies do great with both. If she nurses well, it should not be a problem for her or you!
Not likely. Many lactation consultants and physicians do not like pacifiers saying it leads to nipple confusion. Personal experience does not bear that out...Although there are always one or two children who don't read the manuals(lol) and have issues. A pacifier can be an immense relief for the baby who needs non nutritive sucking. Parents control how long the baby uses it!