When/how do I tell my sister I’m moving?

She knew my fiancé was looking at jobs out of state with the stipulation of 5 years max because they were across the country. He just got offered/is accepting a job out of state but more local and my fiancé told me we’re not moving back home, we’ll be permanently living there.

I told my mom over the phone because I figured she should know. I rarely speak to my sister over the phone(usually text) and she leaves for her honeymoon on Wednesday. When she’s back I’ll already have moved.

My mom told me to wait until she’s back but I feel that’s too late.