What I can guess here is that Nonna is worried that Katyusha relies on her too much or is only comfortable with her only so decides to "ditch" Katyusha to see if she can be left alone, at first her suspicions are true that is until Miho show up and Katyusha immediately gets along with Miho though Clara says something that for some reason shocks Nonna and surprises Miho but the three then head off somewhere. Maho who appears next, asks what Nonna is doing and finds the tall girl trembling with tears forming in her eyes
Sorry for the trouble. That would be of great help.FINDid...Miho-ski!!stpstpstpActually Nonna-san got herself lost, so...
Vertical text, Japanese.Nonna-san did!? Oh no! Katyusha-san? Why are you in a place like this by yourself?I'm sure she's crying by now because her dear Katyusha isn't around for her.Clara!Did something happen...?Oh? You're from Pravda, right? What are you doing in such a pla—Alright, I'll send messages around to our comrades in tankery to have them look for her.