Hi,
I agree with Oion.
In the case of Tenchi in Tokyo, the cels are 
almost all relatively inexpensive, compared to 
other Tenchi incarnations. There are several 
reasons for this, including the number of cels 
still available, popularity and the fact that 
Tenchi In Tokyo has some pretty uneven art, as you 
have probably noticed. :-)
But that character, (which I don't even remember!) 
would probably not sell for more than the other 
side characters...in other words it would probably 
be pretty inexpensive. Best thing to do is just 
keep your eyes open and you will find her!
Good Luck!
Kathleen