Cheyenne is has been on the bars front porch in good springs for the last 3 days and hasn't moved and sunnys not with her nor in the bar. Did she die somewhere or is she just off doing something?

Are you looking for her to do a quest? Or have you finished all the GS quests and you're just curious...

...it's possible she's dead or glitched, yes. Or she may be sleeping/stuck in her house. Anything is possible.

Search around and see if you find a corpse with its head exploded. This may be Sunny Smiles. It happened on my first character, and I looked around and found her outside in the bushes. Turns out she had a nasty run-in with a giant radscorpion. :cryvaultboy:

Sunny had a balloon in her head. The Radscorpion popped it, forever ending Sunny's short adventure with the Courier.

I had that same radscorpion show up, killed Sunny & Easy Pete. Even when I reloaded an earlier save it showed up. That very short attempt at a playthrough was a complete do-over.

Have you done

Cheyenne can sometimes bug and stay stuck in one place for a long time. Did you check Trudy's house? Sunny seems to live there (despite not enough beds) during the time she spends away from the Saloon.

Same thing happened to me, but I don't think it affects the storyline very much.