So, I assume you didn't ever click the [
Leave] option upon encountering her? If you did so after the Old Forest that would explain you not meeting her in the Harvest Valley, as leaving removes her from the game.
If that is not the case and you didn't ever [
Leave] then you could have potentially met her but not recalled the encounter. The way you could check this is, she will be found on
one of the tiles North of the Marefolk village (actually from what I can recall she'll be on the first tile in the Lake division - the first tile you'd step on when coming South from the Shallow Riverbank then going East).
Aside from that, if that doesn't work you'd maybe have to check your save to find any mention of Valencia_Left / Valencia_Leave (not an actual variable, just what it would probably be similar to) or the like.