The sister in law and her fiance going on trips abroad while the speaker is struggling to get their bills paid implies that the former are more wealthy than the latter and hence it is sarcastic to say that the speaker is really happy for it.
Consider the staetement "My sister in law and her fiance are taking all these trips abroad and we are struggling just to get our bills paid.". Based on this statement, is "It's making me feel extremely happy with how my sister in law and her fiance are able to go on all these trips abroad when we're just struggling to get our bills paid" a true statement? Yes/no/unknown