I'm going to defer on this one, because the first thought that pops into my mind may not be accurate...but here it is.
There may be somebody at the gym that she's interested in that she does not want to see flowers on her car.
And I know you know this now, but sending 3 sets of flowers was total overkill. That is major pursuing. I was under the impression that you sent one set of flowers to her.
Let some others give you some input because I'm not really sure at the moment. My first thought is she is telling you to back off.
