Okay PrettyDecent, this is BRILLIANT, because by asking pointed follow-up questions you have forced me to focus on the right things. Up to now I didn't know what the key issues were and was dreading having to post the whole interaction on the boards, which would be information overkill!
It's not (C), let's just rule that out, I can tell you that by instinct, to save time. Good point though.
The other two are both plausible. Permit me a brief but relevant diversion: I had a similar situation to this a few years ago, but didn't know about moving fast, not over-investing etc., so my actions were less assertive, but I did declare romantic interest pretty much upfront. The similarities are worth considering because both situations involved a girl "on the market", having been recently hurt/disappointed by a man, and me "off the market" due to circumstances beyond my control. The vibe is also extremely similar with uncomfortable tension as our interaction becomes more intimate and kino-driven, combined with obvious, unmistakable signs of interest.
In the earlier situation I got follow-up messages saying things like "it's you to blame for putting such a high crossbar for all men trying to get my attention" and "I haven't met a man with a real man-core and real man characteristics inside since I met you". When I called her out on it, pointing out that I had made my interest obvious and she had effectively rejected me, she wrote back "hahaha... usually I'm stone-hearted?

You should guess why". I never did guess at the time, but now that I understand auto-rejection, I suspect that (apart from moving too slow) she found my attainability too low.
Back to the present situation. I am going to skip to near the end, based on your follow-up questions. In the cafe she declined food and said she had to visit a friend later for dinner and to collect a crucial item. Great, so I have clarity on my timeframe. I suggest leaving the cafe and going to a park opposite, as it's a beautiful, cool evening. (This is why I chose the cafe: the park is attractive and offers relative isolation sitting on benches, etc. - certainly enough privacy for a kiss.)
She declines and we walk back to a very upscale hotel where her office is located and where her car is parked in the deck. We are walking at a languid pace, standing very close; I am using leading touch, continuing the mood from the beginning of the date when I had given her an immediate cheek kiss and steered her with my hand on the small of her back. I persist again en route for her to stay longer with me. She says there will be other evenings like this when we can meet.
As we reach the hotel I make a third attempt to get her into a private location... there is another attractive garden with fountains outside a major office building opposite the hotel. She laughs: "Why do you want to sit outside? We can sit in the hotel lobby!" Compliance of a sort, I guess... she significantly delayed her departure to her friend's house.
The lobby is deserted and offers all sorts of nooks and crannies. I ignore the armchairs lead her to a loveseat; she sits at a "friendly" distance with her purse between us. I use Chase's line: "What are you sitting all the way over there for? Expecting a friend to join us or something? Sit closer!" and she politely refuses.
We talk for a while, my hand on her arm. She suggests I might be interested in some social events for the international community in our city, which sets off friendzoning alarms all over my mind. I immediately say: "I don't want to do social stuff with you... I didn't stop you in the street because I wanted to be friends, I didn't ask you on a date immediately because I thought you'd be a good friend. I like YOU." Talk about stating the obvious.
She looks at me with a sort of "understanding" expression, and says: "But you're not single, right?"
This is a reference to the approach a couple days earlier; when I first suggested a date, she said "I'm not sure if we should do this...I'm in a relationship" and I persisted as follows:
"Look... I'm kind of attached too..." (this is putting it mildly) "There don't necessarily have to be any expectations, let's just meet for a short time and see what happens." (staring into her eyes) "I'd really like to see you again."
To which she actually replied "Are you sure?" (the first time I have ever had a girl ask me that, and this is one with breathtaking, fairy-tale looks) and then proceeded to OFFER me her phone number unsolicited. I was awestruck, though I didn't let on
Back to the end of the date, in the hotel lobby: she continues, "What is your situation?" I look off dramatically into the distance, then meet her eyes and admit that I am married. She asks: "American girl?" and I say no and tell her. I ask her the same question and she replies that she is in divorce proceedings.
At this point I physically remove her purse and put it by my side, move closer, and put my arm around her. We sit like that for a few minutes. I don't remember what passed between us.
Eventually she grabbed her purse back and got up to go. We spoke standing for a few minutes; I leaned in for a kiss, but as I said, this time she turned her head very pointedly to give me a cheek only.
PrettyDecent, I think you're probably on the money with what you said in (B) about me trying to "save the interaction". But (A) could be a component of it too: I have a history of women willing to consider me for serious stuff, but not casual stuff, in spite of my best efforts

This girl though, I'd happily do the serious stuff if I could, she's very unusual - in a good way
