Creepy Crawlies. Its a main quest
Ok so heres a step by step to hopfully help because I'm not sure just how far u are but I'll start from 1st f***** the spider girl.
So after turning her I to a half spider u must.
•Gain her trust with food so u can f*** her.
•After f****** her, use the Summoning again to turn her fully human.
•Once you have gotten her pregnant, it will take 1 weak (7 days) for her to lay a cluster of spider eggs. (You will not get an alert to her pregnancy, just keep an eye on her stumach)
•Once she has laid the egg sack, harvest it & she will imitate the next part of the quest.
If you want to guarantee pregnancy Enhanced Fertility is you're friend.