GruntZone360, the original webcomic has only released 190 chapters so far (the scanlation has almost caught up) so I can't say for sure. But nothing in the raws makes it look like a rival female is appearing yet.
I agree with Purplelibraryguy that a sudden dramatic shift in Sooah's popularity seems unlikely, especially as no reason beyond better hygiene is given. But it's now obvious why she "befriended" Mirae--she wanted to make sure a girl she perceived as less attractive than herself was always by her...
This story really reminds me of Pride and Prejudice, to the point where I wonder if the author of this webtoon is doing a modern, Korean version of it. Anyway, I'm enjoying it, though I find the main character somewhat frustrating.