Can I give my baby her pacifier at night?

Yes. Pacifiers do actually pacify infants & there is some data suggesting they help decrease risk of crib death when used as a sleep aid. That said, baby can develop a habit of needing it so much at night they wake you up crying until you find it and reinsert it.
Yes. Up to one year of age pacifiers may be helpful against sudden infant death syndrome. If it helps your baby sleep, continue offering it until this age. Then reduce its use or remove completely.