Yeah, someone said something similar in the written update and I totally agree. If these grandparents had no objection to Satish marrying the divorced (well, she's not even that yet, so essentially MARRIED) woman herself, why oh why would they have a problem with Satish getting married to the divorced woman's SINGLE sister?
Come on Sulochana... I know she's not some omniscient crazy-smart woman, but she must have some common sense.
You never know though, maybe she got it and that's why she said no to Bhavna, but she just didn't say it aloud? Although I think if that was the case they might of shown her thinking that.
Either way, what a bad excuse. I would have expected master planner/life-ruiner Rasika to come with something better than that.