Yeah, but as boring and generic as "frustration" may sound, it's the only way for me to make these types of romances look, let's say, natural. Think about what alternatives we have in Amber's case
1st Amber is so eccentric in her experimental methods that if a patient's treatment requires fucking him, she will fuck him
2nd Amber has mental problems herself and is absurdly obsessed with caring for someone after some time she will put Nika head to her nipple and start talking with a sensual voice ''suck my poor thing, mommy will make you feel better''
For me, the only natural alternative to frustration is when a mature woman is depressed herself and the young MC is the one who is more active party in the affair, first he shows concern, then he hopes that his person will help in the treatment of the disease, he doesn't even notice, the concern turns into an affair.
But will it work in this case? So far, Amber doesn't look like she has problems with depression herself