I was able to trigger the scene "Pregnant Victoria in Black Lingerie" visiting the rent house.
• I gifted her the Black Lingerie
• Completed "Win back Victoria"
• It triggered some days after paying rent to the Guard (I guess the number is not important).
• Not having sex with her for 2 weeks could be a requirement.
• I slept for a new day and slept 8 hours more (may be unnecessary).
• I went to the Mayor House, talked with the Mayor and the Guard, visited the dining room and checked the locked bedroom (only entering may be neccessary).
• I visited the Smithy (I though entering another building could be a factor, but may be unnecessary).
• I entered the house, went upstairs and Victoria was there Pregnant in Black Lingerie.
• There was Oral and Sex options.
• The star by Victoria's bedroom window wasn't present when I was outside, but the Light for Spirit Potions was.
• Re-entering the rent house after going somewhere may be a necessary.
Triggering the scene on purpose is kind of time consuming.
I used an old save (before Waystone 2).
The first time was by accident. I had to pay rent twice before she visited again.