On the nikah day when the عقد takes place in the masjid, is it sunnah for the bride to remain at home?
بِسْمِ اللهِ الرَّحْمنِ الرَّحِيْم
In the name of Allah, the Most Gracious, the Most Merciful
The bride has a choice of participating in the marriage contract herself or appointing a wakīl (agent) to represent her and conduct the marriage on her behalf.
If the masjid does not accommodate women, or the bride has a preference to stay home, or if there will be fitnah (trouble and turmoil) created by going to the masjid, then it would be better for her to stay home and appoint an agent on her behalf. If the masjid has accommodations, and the bride prefers to go there, and there will be no fitnah created, then she can go to the masjid.
The appointment of an agent, from an Islāmic standpoint, can be performed by any means (orally or in writing, in person, or over the phone, with or without witnesses). However, having seen several contemporary cases where women have claimed coercion into marriage, we recommend appointing the agent in writing and in the presence of witnesses, in order to protect against any future disputes.
At the masjid, in the presence of the groom and the witnesses (two male, or two female and one male), the agent will say: "I, being the agent of such and such woman, daughter of such and such person, have given her in the marriage to such and such man for 'x' amount of dowry. Then the groom will reply by saying; "I have accepted such and such woman in my marriage in the presence of the witnesses".
Only Allah knows best
Written by Shaykh Umer Khan
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 al-Fatāwā al-Hindiyyah, 1/324