Though "que" can be a trigger for the subjunctive, depending on what is being said, the use of que is not causal and que is used used to introduce subordinated clauses of all kinds. Some require the subjunctive and some do not. In this case, Su novio aparece etc. is not a subordinated clause. It is an indicative sentence answering ¿qué pasa?. "Lo que es triste es que la pobre novia...." is just saying, What is sad is that the poor bride etc. There is a link to 10 videos on the subjunctive from Light Speed Spanish that I posted. Also, if you search Notes in Spanish they offer a free booklet covering the subjunctive which you can download for free.