If Godzilla 2 will have MOTHRA, it will have the fairies?

I don't think so. I am pretty sure that there will be an easter egg of some sort for them though. I do have an idea for how the fairies could work though.

Maybe Mothra is a telepathic kaiju that can communicate with humans when they are sleeping. Maybe Mothra chooses to take the form of the fairies in these telepathic dreams as her way of communication. The reason why she would choose fairies is that fairies are seen as friendly creatures which would calm the person that Mothra was communicating with. That's just my Theory though.

actually its believed Millie bobby brown's character and her mother are basically supposed to be like the twins shobijin/cosmos

Yeah I don't see how fairies would fit into the monsterverse universe. I suppose it's not impossible. But it would seem odd and jaring if they appear, since the monsterverse thus far has not emphaized the more fantasy or magical aspect of kaijus, but more in the form of psuedo-science.

Remember way back in about 2017 when there were casting calls for KOTM? There was a casting call for two twin korean girls. This doesn't necessarily confirm it but its a huge possibility

Well, one can never rule them out for certain at this point. It is possible they could appear, but it just wouldn't fit well with the movie...unless Dougherty finds a very creative yet satisfying way to put them in, you never know. But for now, I tend to be skeptical about them appearing. 

It is entirely possible that they would appear since every time Mothra shows up, they show up. I just think that they won't be tiny women, the movie will probably take a more realistic approach to them.

Just don't get your hopes up about them appearing...