while fingerprints can linger for a while on an object...others using it later on will mess up long standing ones.
What is to be noted is that Sheila only came to whf a few days before so her fingerprints on 3 weapons at least within such a short space of time is noteworthy of being unusual. It is not conclusive but if viewed from circumstantial angle it builds weight as to the contention of Sheila being responsible for killing the others.
Yes, it would be very significant. Unfortunately, I haven't yet seen any evidence that her fingerprints were on two other guns, even though I have asked for that.