If anyone can please explain what determines which dialogue options are available?

For example i noticed when playing Shadowheart that i have some [Medicine] dialogue options, which i have not seen when i was playing some other character.

Is this dictated by her background/race/class skill proficiency, or by my skill expertise choices during character creation - or by what is the total number she has in that skill?

For example if i take a character who has no inherent bonuses to Medicine and i give them a (modded) +30 to Medicine item, will they now have [Medicine] options in the dialogue?

Thanks for explaining.