Wedding called Off, Engagement done in a grand way

M28, F27 - We met in Feb 15 and said yes in Feb 20 and their family came and met us and said to proceed forward in arrange marriage setup. Had an engagement in May 25 with more than 250 people coming for that. We have 5 months more for marriage.

All went well till 15th July. Regular Speakings, call till 2-3 AM, travelled a lot in weekends to movies, beaches and long drive and getting to know each other well. She was too communicative and affectionate. It went way down in last two weeks and all of sudden the girl said they are rethinking about marriage.

I am quite shocked because, it is the girl who proceed with yes and they did a fairly good engagement and we even started purchasing things for marriage. Is this fate or too common right now in arrange marriage setup?

Need your thoughts!