1.It should be "결혼식에" not "결혼식이". "에" is the place particle like "나는 학교에 간다"(I go to school), you can't use the subject particle "이" here becuase "결혼식" is not a subject. 2.It has to be "수진이를" because.... 1) "만나다" needs an object meaning 需要 "object particle을/를" 2) People's names have pat'chim, "이" is usually put to make them softer. "수진을" is also correct, but "수진이를" sounds more natural. Sometimes "수진이" without "를" can be used because the object particles often left out if it is clear in context. \^o^/

그 사람은 내 결혼식에 올지도 몰라(0) 그 사람은 내 결혼식이 올지도 몰라(x) "~에" means "to" , direction .. "이" is a little different from that. In this case, they are affected by "수진", especilly because there is "ㄴ".under the "진" It is the same when you might used ㄱ,ㅇ,ㄹ,ㅂ,... etc under the letter. if you use the letter which is no under spell, you should not use "이", because if you use, its pronounciation is very strange , and difficult. exactly because it is difficult to pronounce, I think. But in this case, you can use "를" instead of "이". 내일 수진이(를) 만날지도 몰라(ㅇ) 내일 철수(를) 만날지도 몰라(ㅇ), 내일 영후(를) 만날지도 몰라(ㅇ), 내일 명수(를) 만날지도 몰라(ㅇ), 내일 철순이(를) 만날지도 몰라(ㅇ), 내일 영훈이(를) 만날지도 몰라(ㅇ), 내일 명숙이(를) 만날지도 몰라(ㅇ) 내일 재석이(를) 만날지도 몰라(ㅇ), 내일 호동이(를) 만날지도 몰라(ㅇ)..... And you can leave out "(를)" And we rarely use "을" above sentence... because it is some strange...