Yes, it does sound like her baby fang just fell off on the one side. 1 down, 3 more to go! She should end up with only 1 big k9 on each side of the top and 1 big one on each side on the bottom for a total of 4. My baby needed to get 3 baby k9's pulled as they were firmly in place (giving her a total of 7) while the one that came off was helped along by playing a tough game of rope tug-a-war with her daddy. He kept pulling the rope upwards...
It sounds like the adult teeth are pretty much set in. If that's the case, you should really get all of the remaining baby teeth pulled before they start decaying and/or trapping bacteria, etc., causing problems resulting in the need to pull some neighbouring adult teeth to solve. My girl had to get two adult teeth pulled recently (2nd round of surgery

)because of the incompetent job and poor judgement of the first vet that did her dental work (he left a couple of baby teeth untouched). And she's just about 11 months now.