Ultimately the choice is yours,
I was in this same situation a few months ago, I 
recieved an email from a person who wanted a cel, 
that I had never even thought of selling, because 
I loved it so, but I looked at her gallery and 
saw that this was of her favorite charecter to 
collect and I ended up selling it for the same 
price that I paid, because I knew it would mean 
more to her than it did to me.
 
There has been one cel that I have lusted after 
for months and so I knew how the girl felt and 
did sympathize.

It killed me to ship the cel away and I still 
feel attached to it, when I view it in her 
gallery, but I am so glad that it is with a 
person that cherishes it.
 
I would not rush the decision if I was you and 
weigh both sides....

if the money is to good to pass up then go for, 
or if the sentimental value is higher, just let 
the person know that if you ever do decide to 
sell it that, you will email them then. 
good luck
Julie