Aaaand I got my butt handed to me by Meiling. This does not bode very well.
On the other hand, I didn't even try to return to the surface first, so I think after leveling up I should get her alright.
Yay for being a noob, there's so much to discover.
Unless if you've already seen all the crying events, I suggest looping around them, you'll find a one-way path, if you see the second crying event, beat Meiling, THEN see the first Crying event, you unlock an optional boss battle.
Ultimately, it doesn't matter, but it helps.
@My progress
So I got lazy on leveling up on 19F and just Millitary Ruled + Spirited Away + Hourai Barrage + Starbow Break/Laveatainn'd my way through the minibosses of 20F, and I got like 20 levels in no time.
Even then Cosmic was a PAIN IN THE ASS to beat. WHY DO YOU HAVE TO OPEN UP THE FIGHT WITH ETHER FLARE AND DESTROY HALF MY PARTY? WHY.
Aside from that... It was fairly easy to map out the entire 19F, just boring as fuck. Now, my way to the Final Boss is open. I'll try her today after some more leveling. Also, I managed to drop a Scourge and an Armads :3
(Flandre with 15k atk is OP.)