Online dating sites can prove to be very successful for finding significant others to share our time with. The only experience I have in this regard is that I have a few friends who have formed successful relationships on such sites.
Some could argue that a 13 year age gap is a factor; others would argue that the age gap perhaps is of no significance; I would be able to see both sides to this story. And at the end of the day, it comes down to what you, as a person, are personally comfortable with and where your comfort zone lies.
With you being an ex-body builder I can imagine for you that fitness and body wellbeing is something that you value. And I can get how Tash was asking for advice around fitness.
Wow. I'm sorry to read that she cancelled the date an hour before you were due to meet. I'd be pretty taken aback if I were you. There seems to have been a bit of back and forth from when the two of you met.
Oh dear. She really sounds like she's starting to smother you. Yikes! Not sure how I would handle someone texting me every hour asking where I am. Don't think that would make me feel all that comfortable to say the least.
She sounds insecure. Insecure perhaps not only about herself and the way that she looks, but insecure in so far as the fact is that you're probably in a lot better shape physically speaking, and perhaps it's harder for her to meet other people, so when she finally met you, it was this massive relief. But she seems to have taken things a bit far ... instead of drawing you to her, she's indirectly almost repelling you with her smothering behaviours.
Her reaction to you going to ER is cause for alarm. It's not an appropriate reaction one would expect, all factors considered - you were in the emergency department! That's a health risk. And rather than first showing some kind of concern for how you are, she flew to accusations.
And I think all of this really stems down to a deep feeling of insecurity. It's almost as if she's thinking on some kind of level that this relationship won't last anyway ... so ... yes, her methods clearly aren't working.
It sounds like you've put up with a hell of a lot.
Yes, in theory I would say there is hope for her attachment behaviours that can change.
I found this Blog here on PsychCentral - I'm thinking "Attachment" in terms of the way that she has attached herself to you. Might be worth the read. There's also a book recommended at the end of the Blog.
Hope the article might be of some use to you in your personal situation.
How to Change Your Attachment Style | Psych Central