Neither of the dogs were growling or yelping and seemed to be having a good time.
That sounds like the important fact. Keep taking Finley and let her play. Though we have only 2+ years of experience with Fuji, who loves her daily dog run visit (and has lots of frisky play sessions), it seems very clear when the play is too much. Usually the yelp or growl will let you know, and if a time is required, step in. Our best results are always with the regulars, both dogs and people. It is clear that both groups need to learn the rules of the run.
Good luck and best wishes that you meet more experienced owners than naive ones. And that Finley continues to be a good player at the run.