I love my sister, but I'm dreading her engagement celebration

My sister sent a photo of the ring and I replied with six exclamation marks. Then I put my phone face down and cried.

I like her partner. There isn't a secret objection to the engagement. What hurts is that they're moving away after the wedding, and she is the person I currently see on ordinary, unplanned evenings. I knew the move was possible. The ring made it feel settled.

At her celebration this weekend, our parents will talk about how exciting everything is. It is exciting. It is also the beginning of losing something I rely on. I'm ashamed that my first private reaction was about my own Tuesdays rather than her happiness.

Should I tell her I'm finding the change difficult, or keep that conversation away from the engagement altogether? I don't want her to read my strained smile as disapproval of the person she's chosen.