for nsfw, i would suggest them doing some kind of cosplaying themed thing, each one dressed as their favourite characters
a funny one would be if one was dressed as the hero and the other as the villain, and their "fighting" have the villain being dominant and smug while the hero acting as if he's struggling and giving his best.

alternatively, for something cute and sfw (or not >:3) it would be nice to see them draw each other, with one being noticeably skilled and the other doing what's basically a child's doodle
(would you do it nsfw, one of those would be extremely lewd, so either the well drawn potrait be in an erotic pose and bedroom eyes or the doodle feature cartoonishly large bewbs).

The second one sounds adorable honestly.

I'd love to see them birthing onto each other!

Like a 69 oviposition.

Absolutely!

Beh posso dire la mia?
Io che amo l'epica classica potresti usare due soggetti tipici dell'epica:

1) la vestizione dell'armatura (in pratica una delle due sta indossando un'armatura per andare in guerra con l'altra che la sta aiutando nella vestizione allacciando le fibie della sua corazza o le sta porgendo le armi necessarie per la lotta)
2) Un duello in cui le due guerriere indossato stanno combattedo l'una contro l'altra oppure fianco a fianco contro un nemico comune (oppure un esercito di creature oscure)
3) morte gloriosa (con le due o con una delle due che giace a terra circondata dalle armi dei nemici uccisi che formano un comolo enorme)

Well can I have my say?
I, who love classic epics, could use two typical epic subjects:

1) donning armor (basically one of the two is wearing armor to go to war with the other helping her in dressing her by fastening the buckles of her armor or handing her the weapons necessary for the struggle)
2) A duel in which the two female warriors are fighting against each other or side by side against a common enemy (or an army of dark creatures)
3) glorious death (with the two or with one of the two lying on the ground surrounded by the weapons of the slain enemies forming a huge pile)

Adelina uses fire and wields a bow and arrow. Petra uses ice and can wield a sword and shield.

I have actually drawn that before a while ago.