You have gone two weeks, do not give it back. She is ready, it is just a change. Try doing something different, if she is falling asleep without it at night she is done with it, it may have more to do with a growth spurtor teething.
Teething can reek havoc on naptimes too. If she is teething try teething tablets or motrin before naps.
The fact she is doing so well at night she just may need naptime changed up a bit.
If she fusses at naps, ignore her, I know that is hard, but at 20 mos she will get herself back to sleep and you are giving her a gift allowing her to teach herself to do it. It is not mean to let her be for a while and teach her at least quiet time and that when you lay her down it is time to rest.
Make sure the room is dark and cool, put on a a music box, fan or whatever for white noise. Change the time of her naps too maybe. I had to adjust nap times at the year mark and at almost two to accomodate them and the changes they were going through.
If she isn't napping try changing her to an earlier bedtime, that way she gets the sleep she needs and you have some time with her sister.
Just don't give the pacifier back at this point. At that age, if mine woke up too soon and were fussy I left them lay there for another 20 minutes and 90% of the time they fell back to sleep. I never did crying it out until way after the year mark but at naps I did let them fuss if they were still tired.