So me and my sister work for this guy and tonight I’m working and I’m staying overnight and tomorrow…

So me and my sister work for this guy and tonight I’m working and I’m staying overnight and tomorrow morning my sister is supposed to come in and relieve me at 9am.... well last night she got food poisoning or something and she says she can’t come in. Me and her are the only ones who nanny his kids so we can’t call off ever!! My sister is crying because she can’t come in but I can’t physically work all tonight and tomorrow till 6pm... I have doctor appointments and everything... I don’t know what to do. I told her to suck it up and come in, I know it’s horrible but I’ve been working while sick too! I just don’t know what to do 😑😑