When I killed Desdemona she exclaims with her dying breath, "Sam im coming home." anyone else get this?

No one knows. She is a rather enigmatic individual so it could be her Synth husband or wife that was killed by people that found out Sam was a Synth for all we know.

Actually...

It was her synth GF before she joined the RR. She got killed (not certain on the specifics). There's a conversation you can have with Dez about it IIRC.

It's her boyfriend. It leaves the rest to your interpretation. I don't see who else could she call before she died.