Dear Saskia:
You read like a reasonable person and it is socially acceptable to delete or disable one’s profile on a dating site when in a committed relationship.
Assuming she really did get attached to the dating site as a way to communicate with others, had a lot of good times doing so, was relieved from her loneliness at the time, she should disable the profile for the sole reason that it is causing her girlfriend pain. This is enough of a reason.
And so, she disabled it but maybe resentful for having done so… you will soon find out.
I think at this point that she does have the choice: to disable the profile or disable the relationship with you.
anita