So I'm guessing she is at your level, or there about, in terms of work position. I mean, she isn't your manager is she? And she isn't your's, is she? So you don't have a position of authority going for you.
And "you keep checking if you are OK". So you had an objection to her behavior, and you didn't manage to establish boundaries on acceptable behavior from her. So you failed a huge shit test there. You don't come of as assertive. I think that should tell you that she's out of your league. That is what I get. I think she would get that too.
So she was interested in you somewhat (leading you on, as you say), and your flirting, and you fail to provide evidence of some the manly qualities she wants. She probably figures she can do better, you I think, haven't grasped she is out of your league. And I'm guessing you haven't managed to get her out for some real dates, eh? And you send her flowers and a card, which she receives in front of everyone!? Dude...
I've read the responses about "women as beasts" and all that. Utter horse shit.
From her perspective, you failed to establish yourself at a suitable partner, failed to obtain real dates, real commitment. So she is looking about for other partners. And you, in front of everyone, drop her roses and flowers which, thb, puts her in a horrible position. She either has to publicly accept your advances and effectively commit to you, or reject you and explain the rejection to everyone, including anyone she might be interested in besides you. And the only way to do that is to explain that the flowers and card are inappropriate, which, they really, really, are. And because they are inappropriate, yeah, that is kind of harassment-ey. I mean, it would be a single incident, and harassment is a persistent pattern of behavior, that is harassment-ey,
Don't get me wrong, I'm really sorry that this has had a negative impact on your career, and I wish you all the best, but based on what you have written this is totally your fucking fault.