It's going to boil down to some pretty simple questions;
1> Does her contract stipulate that the film would be given an exclusive run in theaters? (this is what I don't think we know, FWIW, and "there was an understanding" generally doesn't translate to a win unless you've got strong evidence to back that up)
2> Did her contract stipulate a big part of her total compensation be a portion of the gross from box office? If "yes", then any decision to alter release to cut out/cut down box office revenue can easily be argued as an attempt to limit her compensation against the terms that were understood at signing. I think we already know this to be true, which means I think she's got a solid argument, but the case can be argued either way, if this is all there is.
I don't think ease of piracy is going to factor in at all, since Disney's hurt as much (or more) as Johannsen is in those cases; you'd need to prove some pretty direct animus against Johannsen to make this case; that Disney was willing to hurt themselves to spite her.
If anything comes out to support the first, Disney would lose the case. In the end, it's probably likely they'll work out a settlement; this is just pretty typical legal posturing before the realities come home to roost, at this point.