Actually, considering the requirement to unlock her (buying the one purchase items) appears to be independent of the story per se, it might be possible to do so before ending the main game if one plays v1.30 from zero, who knows. Could also be interesting to see how the new options & mechanics would affect or not early play. Had a random lady (and two dudes
) offering sex in stage 1 to pass for example (though it's no use as you can't examine her yet
)!
Yes, there are some good hints but it ain't blatant or obvious. I only started to consider it from the moment we are presented to Topaz and later with the reveal of Richard's origin.
Ohh, i'll be definitely be waiting for that!