Here's the relevant portion of code that calculates the hidden points:
if vicoria_relation.like >=60:
$ suc_vic_explanations.limit += 5
elif vicoria_relation.like >=30:
$ suc_vic_explanations.limit += 3
if suc_vic_gift.limit >= 2:
$ suc_vic_explanations.limit += 5
if suc_vic_ste.number >= 5:
$ suc_vic_explanations.limit += 5
If the explanations.limit value is greater than or equal to 10, then Vicoria will switch sides. I haven't really investigated all of the variables, but I assume the gift one has to do with giving her all of the possible gifts. The romance novels in particular have a special scene if you gift them twice. The Ste value might have to do with rescuing Ste by satisfying her (I did it by inviting Arion) and not by force. I think the easiest way to get her on your side is just to spam gifts at her, the like limit with them is 70, iirc (giving her a romance novel the second time gives her a flat 10 like, which is how I got to 80 with her). But if you want to save time, you can just edit the values in Save Editor: set vicoria_relation.like above 60, gift.limit above 2, ste.number above 5.
Edit: OK, I just looked through the code to confirm things. suc_vic_ste.number is set to 5 only if you take Arion with you to satisfy her. suc_vic_gift.limit is set to 2 when you gift her the romance novel the second time. If you did either of these and have her like above or at 60, she should switch sides.