As her birthday fell on Friday the 13th this year she stayed home..
That's unfortunate. Why did she stay home?
She's a superstitious person.
Superstitions can be a fun thing to think about, but you should not take them seriously. You should not base your decisions on things that have no actual impact on life such as what the date is. You will lead a much more fulfilling life if you believe in yourself rather than superstitions.
Actually I know the truth and that's why I had a party to celebrate her on the next day.
That's really kind of you for trying to accommodate for her! But she needs to know eventually that superstitions are just for fun before it ruins her life. How about after celebrating some more, you can teach her that a single day can't cause bad things?