In laws pissing me off

So my 2 week old has Hypothyroidism. No biggie she just takes meds and has to have frequent bloodwork. We have an appointment for her today which is obviously very important to go to. Last night I get a text that my husbands aunt leaves to go back home today and they want to see the baby. First off I’m sick and really don’t want to be around people. Second we have appointments that we NEED to go to. So I told my mother in law that last night and she goes ‘well make time to stop by she needs to meet her before she goes’ and when I said I was sick she said it didn’t matter because they weren’t sick. What am I supposed to do. Cancel my baby’s appointments because his aunt leaves today ? I think not. I’m just so upset that nobody respects me enough that when I say something can’t happen they have to make me feel like crap until I cave. Well I’m not this time.