A few thoughts, some more likely than others:
- She's physically unable to have normal vaginal sex due to a medical issue
- She's emotionally unable to have sex due to past trauma and this is her weird means of asserting control
- Her agency insists she can't have physical relationships, and this is her weird way of getting around it.
- She's fully capable of having sex, she just has a weird kink.
I'm thinking #2 is most likely. #1 is an outside possibility. #3 would be weird; she's an actress, not an idol -- they aren't under the same restrictions.
I fear it's just gonna be #4 and the author's gonna be like "don't kinkshame, bro"