Sister in law

So my husbands twin sister is getting married in April... Out of the country... I'm currently just over 5 weeks meaning I most likely won't be able to fly, and will be very close to due date. Hubs sister has always felt overshadowed by him and is also a very self centered selfish kind of person (his words). I'm already stressing about telling her as she will immediately think about how I've stolen her thunder, and I'm concerned it will be even worse if I ask my husband not to go either (if he misses the labor part I'll kill him!)😀. What would you do? How should I handle this?