MacySan
Sumin should not be her god, to the point where she is willing to lose all of her self respect.
well, the way Seju is designed, she has severe insecurities, in a sense that she didn't even feel assured even during her best times with Sumin, flashback in ch56 and again in ch72.. and let alone ch10 and 26.
she herself doesn't believe that anybody would love her the way Sumin once did, and for that she is going to sacrifice every thing she has for what she calls: "the distance where I could feel this emotion" ch45.
if a person doesn't feel worthy of being loved, how could we assume that they have self-respect?
the promises that Sumin made are even more significant to a miserable child like Seju, they were a lifeline to her.. you can see that in the beginning of ch19, no matter how much hate she receives, that one great love made her feel worthy and able to take it all.
but at the same time, she has her pride to show it only and only Sumin is not involved in the picture.