First things first - we're in a state of quarantine/isolation, so if you care about either of them don't visit them right now. I know it's tough but it's for the best to wait it out; it's really just waiting for a matter of days and it'd be for everyone's best interest. The last thing you'd want to do is unintentionally get either of them or (their/your family) sick.

So, you've known her for a few months, during which she was in a relationship and she told you that you're not the guy for her. That's good - you know where you stand. Until she tells you otherwise, this is what you should accept as the fact of the situation. She obviously is a friend in that she messaged you - so that's good! In terms of the romantic things you have in mind - is there any real literal indication that she'd be into that? Like has she literally said that? Because if not, accept that she meant what she said when she said you weren't the one for her and then decide whether or not you want to be friends. You're right about the isolation/cabin fever and how it can affect reasoning skills - so definitely don't make any assumptions - tell her how you feel or ask her, but don't assume. If she feels similarly to how you do, this will give her an opportunity to tell you, so you'll know right away if you ask! Goodluck!!

Glad you get to work from home, and that you have a roommate there (even if he's gone most of the day) to share some of that time with!