But Starman didn't have a 'wife' or anyone at his home planet. He indicated that to her when she asked.
You could be right about his looking like Scott. Good theory.
But I still think she came to realize that he was in fact his 'own' being. And she cared for him, knew he cared for her.
I'd say this cloud is Cumulo Nimbus.
Didn't he discover America?
Penfold, shush.

i suggest, but dont insist, that that idea could be written in or out of this story.
if the baby could not endure the starman home planet, then jenny could be told it would be hardship for her physically but as an adult she would live a normal lifespan. assuming time were calculable in a comprehendible way. of course starboy would know. we think.
if both would survive but have hardship, then starguy was saving them pain. the price was that they could not all coexist in some form of comfort on either planet. the obvious problem for him was earth conditions did not allow him to survive even tho he could somehow take on the appearance of those who had died a short while before.
the story could have been written allowing them all to leave. as in close encounters.
it wasnt. the story satisfied enough expectations of a satisfactory ending given the terms of the lives. anyone care to suggest alternate story lines to conclude stardude, please speak up.

Except Jenny had already acknowledged that she knew what they had was temporary when she asked if he had a wife at home. She knew and was OK that he may have other commitments. She really was still seeing him as her dead husband. If he'd looked like any other human, I doubt she would have developed feelings for him.

It wasn't so much that she didn't care about the baby. Its more like what others have mentioned:
She knew she was never going to see Starman again; not only was he 'like Scott', but she loved HIM. Starman. Even as an alien.
Jenny knew it was her last chance, she was basically saying she would rather go and both she & the baby die with him than stay on Earth without him.
I'd say this cloud is Cumulo Nimbus.
Didn't he discover America?
Penfold, shush.

You know, I watched this again last night.
Alright! I've actually watched it a couple more times on TV in the past week.
I've came to the conclusion that the purpose of the scene and indirect result of Starman's form is that Jenny gets to say goodbye to Scott, by teaching Starman how to say goodbye. Which he does by professing his love.
I now see Jenny's line as totally authentic. She's professing her love for Starman in proxy for Scott by saying that she doesn't want to say goodbye and wants to be with Scott whatever, wherever. That she will go on alone doesn't mean it's a hollow sentiment, because ultimately she knows she has something to live for.
At least they both get to say goodbye.
Glasgow's FOREMOST authority
Italics
= irony. Infer the opposite please.

This message has been deleted.

After "Scott" convincing Jenny that he has impregnated her with Scott's baby I have a hard time accepting that she doesn't care about not living anymore after that moment without "Scott".
As much as I like the line, you bring up a very good point.