DonkeyKong just nicely laid it out. I've watched way too many of Dorte's games now, going back to when they were down in the 100's for elo, and I will stress the part I and others are latching on to: Dorte sometimes chooses to roll when already having capped another column, and when she does so, she never busts, to an absurd rate in a short period of games.
I've gone back and watched many games where Dorte isn't cheating. They behave like a normal player in a great many of those games--she busts early, stops at reasonable progress. Critically she also often does stop after capping one column. There's quite a few games where Dorte has the option to just keep pushing for a win in a single turn and decides not to, instead behaving like a normal player. (In fact there is even one game where Dorte probably should push for the win and doesn't!)
I think the particularly odd part of Dorte's strategy that we're all latching on to is watching Dorte not only push some number combinations far further than one probably should (although they do this pretty often), the truly alarming bit is that even after they manage to cap one column on some of their spurts, they keep going--and never fail. These are the critical pieces that make it fairly clear Dorte is cheating--you simply cannot consistently get in a position where you've capped a column and just keep pushing to roll and literally never busting. The odds of Dorte achieving this string are unfathomable.
Again, I think it also is a really telling sign that Dorte does not normally employ this strategy--she has plenty of games prior to this sudden winning streak where she does not do such things and instead stops after capping one column. This streak repeats last season which is what this thread started on--Dorte has another run last season employing this strategy and never failing and shooting up the rankings to win arena, and now we are seeing it again. This is just altogether far too much to chalk up to chance--even if you assume Dorte is the luckiest player ever, why does Dorte typically not employ this strategy, but then suddenly does and manages to never bust? There's a few games in there too where Dorte is capping 4 columns--a strong player would generally never roll again and risk losing out yet Dorte does. The only way to rationally explain Dorte's actions when they already have capped at least one column on a turn and yet continue to go are because Dorte knows they are not going to bust.