COVID-19 - how do I navigate this situation with my advisor?
As someone who's been out of academia for a while, I would like to offer a different perspective. Yes, occupying your co-advisor's attention when the roof is on fire is tone-deaf. However: you have acquired skills that are obviously in high demand these days, and are thrown into a (hopefully) once-in-a lifetime situation to apply these skills. Especially since you're not on a strict deadline with your thesis, there are now more important things than finishing the thesis at the scheduled time. See this as an opportunity, not an obstacle.

Check if this is okay with your primary advisor, then send a mail to your co-advisor saying that you would be glad to put your thesis on ice and help her with her COVID work if she has anything you could be of help with. If you are a capable student, she probably will.  

Then, when things have calmed down, reevaluate the situation, see what you have learned in the meantime, and continue from there.