We know they've been living together for 2 years (time skip).
Are they a couple?
I mean, 2 girls living together means they like being with each other. They must also like each other as individuals. Liking leads to feeling love. Feeling love leads to making love.
They're not a couple. They are friends. I live with another dude. We pay 400 dollars each to rent an apartment close to our university. And I assure you we're not a couple.
Wendy and Chelia have always been stated to be friends. Also, one of the last chapters has disclosed and confirmed that Wendy has never done anything sexual with another human being (chapter 508). It's a confirmation, Wendy and Chelia are just friends and did nothing sexual (not even a kiss) during that year.
There are just 2 hints that may lead into thinking they're a couple:
That they lived together for 1 year. As I said before they didn't do anything.
The famous quote: "Don't cry, Wendy... Even if I don't have my magic, at least I'm still alive... And love is way stronger than anything magic could offer."
It is exactly how it sounds. Wendy was going to die and Sherry saves her, but she loses her magic. The "love is way stronger" can be interpreted many ways, and most aren't yuri related. Since the beginning of the series everyone says love is the strongest force and it's usually not related to love affairs. Ultear sacrifives herself, Lucy almost dies a few times trying to protect Wendy... protecting each other is something Fairy Tail does with everyone of their members regardless of gender. Wendy joined Lamia Scale because Fairy Tail was disbanded and has been part of that Guild for a whole year, more time that what she has spent beeing a fairy tail member.
In the future the author may change that if he wants but so far they are good friends.
There isn't one single romantic moment between Wendy and Sherria in Fairy Tail. The most you'll find is them being good friends or protecting each other, something done by everyone between members of the same guild (Wendy joined Lamia scale for at least 1 year).
What is romance? Romance is for example Erza and Jellal. Erza was worried her body wasn't good enough for Jellal when she got shrunk. At another time they almost kissed while looking at each other lovestruck. Another less clear example is Lucy. She blushes because of Natsu, when she thought he liked her and she imagined themselves dating and was disappointed when she found out the truth. Juvia and Gray is another example. That is romance. Simply protecting each other is not romance, giving your life for your friends is the standard everyone follows in Fairy Tail, although they almost never die.
Some people say they're more than friends because there's a tweet where they are playing with water and there are other people that have been portrayed by Mashima to like each other.
The tweet is not canon.
As I see it, a good reason for her to be included there is that she's one of the main characters just like most of the others. It's not like they're doing anything romantic anyways. Erza and Juvia attack their men in a romantic way. Lucy and Gajeel attack their "potential" partner physically, something like teasing. Wendy and Sherria just play like normal friends.
Actually, I think I am overthinking it. Mashima's tweets/drawings outside the canon world usually lack common sense or are fanservice. He's drawn Natsu and Gray saying I love you, boys' love between Gray and Lyon, Lucy and Aquarious...
If you're looking at his tweets expecting everything to be a good representation of Fairy Tail you're up for big disappointments in the future. He likes mixing reality with illusion.
Short answer: No.
However, it's been hinted by Hiro Mashima on his twitter. He does this thing where he'll post pictures of all of the "couples" ex.
Natsu and Lucy, Gray and Juvia, Gajeel and Levy, Erza and Jellal, etc.
In one of his more recent ones he included this picture:
This is also not the only example, if you scroll through his twitter. So while it is not canonical (just like all of the other "couples") Mashima does hint that it's more than just a friendship.
