story identification - A girl who transcends time

I remember quite a bit, but can't seem to find the title or (female) author.

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  A girl accompanies her father as he captains a mission to travel at near-light speed in order to experience the effects of time dilation and return to Earth 100 years into its future.

  
  


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  She leaves behind her boyfriend (Tal or Tel or something), who promises he'll find a way to stay with her despite the time travel that will render him, well, dead before her return.

  
  


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  She's accompanied by a close friend who is deaf but lip-reads and speaks so well as to occasionally fool others into believing she is hearing. They spend a lot of time in the ship's garden.

  
  


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  I believe he ends up either getting on a different ship to survive into the future via time dilation, or else having himself frozen.

  
  


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  Either way, if I recall correctly, Earth isn't doing well at all by the time the mission with the girl returns. There's been a war or some other disaster.

  
  
  


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  There's an extended period of vague, ambiguous, existential crap in which the girl (now a woman) eventually ends up transferring her consciousness into her own daughter, presumably in order to go on living.

  
  


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  Everything wraps up somehow and the girl and her boyfriend walk together hand in hand on a desolate planet into the sunset near the end of time.

  
  

It was all really rather trashy and silly, I remember, and took itself entirely way too seriously, but I'd like to at least know what it was so I could read it again. Either it'll be worth a laugh, or it'll turn out to be surprisingly good.

Answer

I don't think this is it, but it's been a long time since I read it so I'll throw it out anyways... there are some similarities, and it's possible one or both of us might not remember the details exactly. :)

The Starlight Crystal by Christopher Pike.

Short trashy novella about a girl who transcends time on a space ship that flies at near relativistic speeds. The story starts with her meeting a mysterious older woman, and then later on she's the last human alive, throws the ship into overdrive, and actually loops back around in time and meets herself...

I do vaguely recall something about a boy being involved.

EDITED TO ADD: An Amazon review says the boyfriend's name is Tem. Maybe this is it. :)