One thing came to my mind is that Archana is protecting her daughter and anyone who is against Purvi is not spared today. But when she will come to know about the fact that Purvi really loves Arjun, what will be her status of mind. She has lot of faith on Purvi - and it gives very positive vibrant in PR.
Archana is totally unaware about the fact.
The party is not the right place and it is also not the right time. Purvi should say everything before hand. When Archana will come to know that Purvi has told her lie & hide the truth, she will be feeling isolated & mentally shattered.
Mother daughter relationship is so pure, but sometimes circumstances make us guilty. If some one close breaches our trust , it is very tough to recover from the pain. Purvi is feeling the pain. The same pain will be felt by Archana coz it is very hard to adjust that some one close to my heart is hiding some truth from me or telling lie to me. There is a thin line between hiding the truth & telling lie. Once this bridge of trust is broken, it takes life long to build it again.