Baggage allowance

My other half is going to be travelling SFO-LHR-DEL. I was wondering if anyone knew what her baggage allowance would be? (she's going to be doing a lot of wedding shopping!)
I'm pretty sure that if all legs are on the one booking, the two piece allowance will apply to the LHR-DEL leg as well.
However, is there a limit as to how long she can stopover for in the UK on her way to India in order to keep the two piece allowance (as opposed to 23kg LHR-DEL)? I'm hoping it's longer than 24 hours!
Cheers,
Neal
I'm pretty sure that if all legs are on the one booking, the two piece allowance will apply to the LHR-DEL leg as well.
However, is there a limit as to how long she can stopover for in the UK on her way to India in order to keep the two piece allowance (as opposed to 23kg LHR-DEL)? I'm hoping it's longer than 24 hours!
Cheers,
Neal