Sitting in the dark...

So my 9 month old baby is on a pretty good schedule. We start winding down for bed around 6:30. Takes a bath, reads a book, cuddles and a bottle and usually asleep around 7:00-8:00. Well, at 5:30 my MIL decided that my child needed a nap even though I told her not to lay her down. Long story short, I’m sitting in a pitch black room at almost 9pm because my baby is wide awake and not wanting to go to sleep any time soon. So my question is, how do I deal with a mother in law who has no respect of my schedule for my baby and a husband who allows her to overrule me when we are visiting? Side note: My husband and his mom were both born in Mexico and there’s a strong language barrier between she and I. My husband translates our conversations and I don’t really know what he’s saying is exactly what I’m trying to tell her