firstly, hello i am in love with the way you've put his bio together. secondly, the line involves some duplicity on marisol's part as she was dating this person with the singular intention of using them to get closer to or gather information on a target within their proximity, only to disappear once she had what she needed.
so! erich's standing within the music world would make him a good target/candidate, imo, whether it's his time at the met or beforehand. it would have been a seemingly legitimate relationship with marisol committing whilst secretly holding back (and ultimately ghosting), and leaving herself with a good amount of guilt that she doesn't want to cop to. his relationship with substances and such would 100% make her feel worse because there's a what if to be asked that she doesn't want to ask! if you're down, we can obv hammer out more details about the relationship, timeline, how they'll come into contact with each other, etc etc