@Earthliŋ 「信用できる」って言葉です；"believable / credible" つもりで言う。「信用」＋「出来る」じゃないけど、「彼女が信用できる」＝ "she is the one that (is believable)"。
I was confused at first because I thought it was 信用 + the verb 出来る but turns out that 信用できる is just an expression on its own meaning "believable" or "credible" or similar, so it would be ～が for "she is believable", whereas ～を wouldn't really work since a) it's not transitive, b) it wouldn't make sense to be the object of "to be believable", and c) it's not really actually a verb per se but just an expression
