Guys, guys… Obviously, anyone wants to be a lesbian with Orin okay?
But if seriously, it was just a phraseology. Canonical Marrow is bisexual. We also mentioned her platonic bond with Gortash. But she had no experience of a normal serious relationship before Astarion (if their relationship can really be called normal lol) because she is Dark Urge and was the head of Bhaal cult — a person who was not looking for anything healthy and good

So with Orin, they were just physical lovers, not patners or more. But they could potentially be if everything were different