It does seem like it contributed, not because of the sexual nature, but because of her essentially playing out a lovable alter ego who is much more together than she actually is and beloved by many. She did this in the tutoring and even in her personal life to an extent, but there's still more of an expectation for her to be "herself" there.
If we think about the stigma of the work as well, even in the US (my personal nationality) but especially in a somewhat more conservative country, this is a pretty big psychological burden as well. You have this secret that, if people find out, could change how everyone in your work etc see you and carry that with you in every interaction. There's a level of constant stress with that sort of secret that most people would not be able to understand.
I think having these three personas has led to her having a fragmented kind of identity where she must be all things to all people while not being sure who she is in reality. This leads to her feeling empty and trying to define herself in relation to her sister, only for the sister to fill the role she wanted with someone else. That is when she became suicidal, as she had nothing to work towards (similar to Makino in the beginning) or define herself by.
Now she's at "I seem to be helping Makino and I could still see this university plan through longer and see what happens before I permanently call it quits," which is not exactly Prime Mental Health, but it gives her some level of purpose to her day to day life in terms of why she's doing things like studying or working to begin with. I think she will probably be feeling a lot of pressure to be "Makino's ideal girlfriend" and mold herself into that entity, even if Makino doesn't have that kind of expectation herself.