OP, you have my sympathies. I would go insane.
I am a stay at home mum, spend a lot of time with my children, taking them places, homework, games, etc but we also have rules. Table manners (and general manners) and bedtime is compulsory. I would never accept my children trying to hang out with me and my husband (their father) past 8/9. And if I was away with a friend, that would be 8.
My children are older, 8, 10 and 12 but they know that after bed time, they can quietly read their (no Internet) kindles in bed. And no talking and there will be trouble. But they have unlimited books and can read until they fall asleep on holidays.
I have no idea what I would do in this situation. I would probably kindly explain to Alyssa and her mum that after 8pm I was in adult only mode. And pour myself a glass of wine and watch Netflix (something completely inappropriate for children) on my phone/IPad for an hour or two, refusing to discuss anything child related. And then go to bed if the child was still up.