I forget.

Is there a reason Linda can’t do it?  She’s got Martian DNA.  She’s got — oh, right, I think you need Alien Abductee powers or something.  I think both were necessary.  And, uh, I guess for whatever reason, Head Alien wouldn’t give Linda an Alien tune-up?  Because he’s a dick?  I dunno.

Or maybe Linda just thought she might be too old, or dead.