I think your mentor's correct. In my limited experience, if one is lucky enough to catch the first swarm out of a hive and get the old queen with the group, you're up and running pretty quickly. But if the swarm was a 2nd or 3rd (or so), then the possibility of getting a new queen is higher. Three to four weeks to get her out, mated, ripened, and laying.
If you don't know where the swarm came from or how many times that particular hive may have already swarmed, it can be a bit tense making yourself wait the alloted time to know for sure.
Not saying that the weather isn't a factor, it very well could be, but timing as you lay it out seems about right. Sounds like she's a good layer...congrats!