The clue is "What is 2 5 1's 10th?"
The numbers are spaced, suggesting they have meaning of their own which would be disrupted if pressed together, ie, they are not the same as "251". Also, I am pressed to think of something other than a person that would use a possessive apostrophe. It occurs to me that using a simple alphabet cipher, 251 spells "Bea", which is a shaky conclusion, but not without merit. Since Bea has not (to my knowledge) written in the contests, I thought it might be her posts or her likes.
The 10th thing Bea liked was a post by Jmack on Jane Austen & Goblins:
http://fantasy-faction.com/forum/work-to-be-critiqued/goblins-jane-austen-just-for-fun/msg96616/#msg96616The 10th like Bea received was for a post about the forum's Karma System:
"But... but... now it almost looks like the bad F site

I only like one F site, the F-F one, of course

Eek, now there's a big red like button next to each thread! Please can we keep them just for posts (if we must really have it)?"
Bea's 10th posts appear unaltered and are as follows:
Counting backward, her 10th post was about butterflies:
"but... but... Schmetterling is also a nice word, all fluttery

I mean, if you're looking at it, Butterfly? butter+fly

(in portuguese it's Borboleta)"
Counting from her joining the forum:
"I'm reading 'The long earth', by Terry Pratchett and Stephen Baxter. I wanted to like it, but I just can't get into it... So, they're 2 english authors, but it's such an american book, it's putting me off.
I'll finish it, but I don't think I will bother with the next volume

Back to fantasy after this one... much better, hehe"
If this is a dead-end, my apologies.