In yesterday's scene, Jeevika first promised her parents that she will fill Manvi's life with happiness but then she also points out the promise which she has made to SB. So why did she look at her wedding photo and remember the event in flashbacks? My guess is because it's to remind herself that she is a married woman and she had taken some vows and that she has a duty to fulfil as a wife & Bahu. If she was going to leave Virenji, wouldn't she have remembered her other memorable times with him? Why did she just remember the wedding? It was more of a reminder because SB's accusation of Jeevika only thinking about Manvi pricked her.
Not that this takes me any closer to what the promise is about but it definitely seems more Manvi related because she is promising to make her happy but possibly restricting her ways somehow.