I just wanted to add that we aren't privy to the nature of the conversations OP and the girl have had and we must be careful that we're not projecting onto the relationship and presupposing a deeper connection than what we ourselves would develop before we declare that we love someone. All we have is OP's word and general descriptions on whats going on... and he's pretty open in admitting that he falls hard very fast. We've also seen glimmers of the casual nature of this relationship as well (OP is still 'browsing' around on Tinder and open to connections with others, her suggesting threesomes, OP being open to such arrangements, etc.) so this already suggests something funky going on with everyone's expectations. If he's telling this girl that he's ok with keeping in casual and then giving her ultimatums and crossing over boundaries he previously respected (re: her alone time and needing to meet him before she decides how she feels) that might put her hackles up... especially if she had any earlier misgivings about the relationship that we don't know about.
So much depends on how things are communicated too. Different people can have different definitions of what 'calmly' and 'reasonably' entails, for example. (I will never forget a friend describing her reaction to something happening on vacation... and then being shown video evidence that wildly begged to differ lol. People generally try to present themselves in the best light).
The funny thing about human nature is that even when we're not feeling that strongly about someone, our fear of rejection may have us grappling for their attention and conflating that desire for validation and certainty with our feelings for them. And sometimes the bigger the insecurity, the larger the imbalance in our behavior.
And there's a lot of imbalanced behaviors out there that give us reasons to be cautious and blow on cold air. Especially online. There are exceptions, of course, but generally speaking.... how well can you really *know* someone until you spent some time with them face to face?
Yes. This. And besides people showing you their best, I think its also easier to project onto someone online than it is offline-- and not just in terms of the best, but the worst too. I think it's healthy to be cautious and not get your hopes up (or down) straight away. People move at different speeds. You generally want to pick one that's along the same wavelength that balances the both of your needs and has you meet in a middle that's comfortable for both. If there's an imbalance there, there's your first hurdle in the relationship and so much is going to depend on a person's previous experiences with this exact thing.
At this point, it's best to just leave it and see what happens. OP, you've said what you've needed to say and now that ball is in her court... as intended. Hopefully, the connection the both of you have described will carry you both somewhere positive when you do meet.
In the meantime, it's out of your control now. Finishing purging whatever frustrated emotions you need to purge, and try to focus on something else.