Sellin is worried that the door of her sister's cabinet is hard to shut 需要多一点的语境，不过字面上大概是这样吧

I guess what the writer wants to express in a humorous way is: "赛琳 thinks that her sister will come out of the closet soon". or " 赛琳thinks that her sister will confess to the family that she(her sister) is a lesbian soon." PS: 出柜 come out of the closet

赛琳 is worried that the door of the dresser/cupboard/cabinet/wardrobe (needs more context to to know what it is) is not closed/shut properly

where did you get this sentence? I meant to put it in comment. oops.

我觉得这个情况要多点语境才翻译过来。不然应当很难了解。 私信我吧我来帮帮你