Personally, I'm fine with pacifiers as long as yr kiddo dont get addicted to it when he/she grows up. I tried giving dear son pacifier but he prefers his thumb even though I was bfing that time.
The only problem I can think of for your case would be nipple confusion coz you're still bf-ing yr baby. Yr dear daughter might get confused if you gonna intro pacifier but not 100% all babies get confused. So it's a 50-50 thing.
It is also a good thing that your baby is suckling at your breast coz in the same time, she is also stimulating your breast for more milk supply! Just let her latch on to stimulate for more milk supply.. Pacifers let her use when she is gonna sleep only. When she is asleep, take it out or it will drop out. *relax*