oops, forgot I had left that in my description.
I joined the site with my photo a few weeks ago when we had 'split'.
I removed all that afterwards when we worked things out. Kept it up because, I
agree, things don't look promising at all, all too often.
She is in her early 20's and yeah, pretty immature.
Which demonstrates thoroughly that, regardless of how ridiculous her object of choice was, her feeling of insecurity in the relationship is well warranted. You've already created at least one exit, which you fully expect to use. Also, you have no respect for her, hide things from her, and don't take her seriously in general. Some of this may be warranted, but that doesn't matter - it's no foundation for a relationship.
She may be unclear on why, but she knows the connection is tenuous between you. You can expect pretty constant drama because of that as long as you're nominally still together.
So do the grown-up thing yourself and break up with her already. That'll prevent any further meltdowns over unrelated trivia. I'm sure she'll have some break-up meltdowns, but at least they'll be about the actual problems. They'll also be over, and permanently, in pretty short order, relative to what you can expect if you keep stringing her along.