I think it’s better not to lock friendship or romance behind stats, but make stat-based options to interact with characters.
For example, if your character talks to Princess Fluffyflowers, who is compassionate and studies nature, your options can be like this:
"I see some healing herbs growing here! Nature is both beautiful and good, isn't it?" says Fluffyflowers.
Your response:
*choice
*if (nature_knowledge > 50) #Start an intelligent conversation about flowers.
You talk about flowers for hours. Looks like you have a common interest.
fluffyflowers_rel +20
*goto pick_flowers
#Yes, that's great.
fluffyflowers_rel +10
*goto pick_flowers
*if (ruthless > 50) #I hate flowers. Healing herbs are for weaklings.
Only strong people who can heal from their ruthless spirit deserve to live!
"You are so ruthless, ${mc_name}!"
fluffyflowers_rel -50
*goto fluffyflowers_runs_from_you
*if ((ruthless > 50) and (speech > 50)) #I think nature is dark. Like my tortured soul!
You start a passionate speech about your dark past, hinting that only Fluffyflowers' love can redeem you.
"I can't change you, ${mc_name}. You should work on your character flaws yourself!"
fluffyflowers_rel -20
*goto fluffyflowers_runs_from_you
*if (ruthless < 50) #No time to talk! Our friends need these herbs.
"You are right, ${mc_name}!"
fluffyflowers_rel +20
*goto pick_flowers