User blog comment:IamJakuhoRaikoben/Chapter 422: Orochi's Fin, Review./@comment-5303512-20150302232516/@comment-7418318-20150303121848

It could be several things that might be the reason for this different behaviour.

The easiest (and least interesting) reaosn would be that unlike her cousin Chelia grew up and thus stopped being overly jolly and throwing around the word love no matter of context.

More likely in my opinion though is that one of the following:
 * Chelia sensed that Wendy isn't really happy in Lamia Scale and is either secretly or subconsciously longing to be back in Fairy Tail. And she feels like Wendy only stays in LS for Chelia's sake, making her feel responsible for Wendy's misery.
 * Despite her words Chelia is afraid that Wendy will leave her.
 * My last one is gonig at the title of the next chapter: Over the last year Chelia's deep friendship to Wendy turned to something more and she fell in love with Wendy, but she couldn't bring herself to tell it (most likely out of fear that it might ruin their friendship - the usual animanga cliché I suppose). Out of fear that she might give away her true feelings she grew a bit more withdrawn.

Personally I hope for the first one of those three, sicne it would allow Wendy to leave without any regrets. The other two would mean that most likely Chelia's left behind somewhat heartbroken, whether it's just friendship or outright love.