vibe check (stolen from twitter user scarmarket)
okay for a longer answer though: my answer is still gonna be vague. i do not know if we got like more 'proper' indepth details about how exactly her arts work in ch12 story so take things i say with a grain of salt. but it essentially really does boil down to a 'vibe check' and with her profile/lines we at least know it has a rather big extent to what she can figure out about a person (like, it's more than i would've thought). Ines sees people's "shadows" (kind of how they are as a person, their intentions) and sometimes describes them in really specific kind of ways (the whole pawn talk about Doctor and ruins about Talulah).
With her arts she figured out things such as rhodes island's whale skeleton and saw 'two shadows' regards Talulah. One of her voicelines talks about how her eyes tell her that she can see what has changed (in regards to Rhodes). Other things include figuring out people's deepest fears and joys, so her arts can just kinda...figure a person and their emotions including really indepth ones out.