BLR does not have a BA arrivals lounge.
Are you sure she needs a test when she lands rather than getting one in UK?
The last I read was that passengers flying into DEL or BOM require a PCR test on arrival. BLR and HYD passengers did not need one on arrival the last time I checked.
It would be interesting for me to know too as I am due to be on the same service in a few weeks again.