On the positive side, you know what you're dealing with now & you know not to accept any more donations from your friend!!
This. I need to acknowledge the emotions around this. I'm pretty dark at her - laugh at your non-housework all you like, but don't go making my life harder!

I did a bit more searching tonight and I don't think we've got it too bad. It doesn't look anything like the images on Google! If I didn't have the bites for evidence, I wouldn't know. I went crazy vacuuming today, and I'm going to steam or freeze all the soft toys and probably a few other things that were in their room. We will try diatomaceous earth. And I'm pretty close to replacing the single bed mattress anyway. The cot mattress is a tougher call as we're nearly done with it.

We don't have a dryer, but I'm going to see what I can arrange.