In the situation, 화요비가 부르는 것 같아 is more natural as Korean is listener-centered. A. 화요비가 부르는 것 같아 I think you sing like 화요비 B. 화요비가 부르는 것 같은데 I think you sing like 화요비 I'd be inclined to say 'B' because it sounds a bit softer than 'A'. Saying 'A', you're just saying what you think - But saying 'B', you're implying you want the friend to say what she thinks.

Actually, "화요비 듣는 것 같아" isn't natural in that situation. 화요비 목소리 듣는 것 같아 or 화요비 노래 듣는 것 같아 is more natural. "화요비 듣는 것 같아" sounds like you are listening to a person not the person's voice. That's why you have to put "목소리" or "노래". Anyway, if you want to show exclamation, you can use like "화요비 노래 듣는 것 같은데?" You have to put a question mark(or sometimes with a exclamation mark). "~같은데?" is idiomatic ending of a sentence when you show your opinion. It is similar to a tag question. Sometimes, "~같은데..." is also used in same case, but "같은데..." is less confident expression. For example, 1) 화요비 목소리 듣는 것 같은데... 2) 화요비 목소리 듣는 것 같은데? 1) means "I think it sounds like 화요비's voice.(but I'm not sure.)" 2) means "I think it sounds like 화요비's voice. (don't you think so?)"