I believe that a discussion between Haley and Haley II is inevitable and essential to the resolution of this story, and to the salvation of both girls (regardless of whether or not Klaus has already had his way with Haley II).
As for Haley's reticence to talk to the MC about Klaus, I don't believe that to be a permanent decision. Haley has already gone from saying that the whole thing was her fault, to admitting to the MC (and to herself) that Klaus had hurt her. Indeed, I believe Haley is already well on her way to realizing the self-deception she had been living under, which is an essential step in any recovery she is to make. So, Haley may yet unburden herself to the MC, regardless of what she says now; perhaps after meeting with Haley II. It's all part of her growth and recovery.
In all of this, the MC will have an essential role to play, as he (through our choices) supports Haley during this period.
Having played through both versions (Sandra/No Sandra), I now believe that a successful outcome (Haley 'cured', Klaus receiving appropriate punishment, Haley and the MC together) can be obtained in both routes. After all, they both end with the same discussion - verbatim.