The event of meeting her briefly has to do with Tanya. Basically it all comes down to this:Can someone help me? I want to progress Eva, but all the guide says is "you'll briefly meet Eva soon enough" but nothing is happening after a multitude of days, so I have no clue
When playing Lewd Town Adventures, please make sure you’re visiting the girls in the journal every couple of days.
If you skip even one character for any reason, you possibly may encounter out-of-order events or lock you out of progressing the rest of the game.
Certain characters' storylines are interwoven so much that avoiding one specific girl for any particular reason could possibly break the immersion and sequential flow of the stories we are telling in this game.
There are a few cases where this is possible, the coming update I'll improve it a bit to make things even clearer.
In general, things are pretty smooth though so that event will trigger after doing a few of the other character's events.