The only BP check is at the T5 transfers desk. It may or may not form part of some conformance check - I'd be interested to know.
But if Mum's flight is disembarking at say t-30 I'm sure they will have someone to meet her off the plane. The bags would be the concenr there, I dont know how that works.
If it's too late to get to the departing DOH flight there are plenty flights each day to ME destinations so she'll get there, albeit maybe a few hours later and with an extra stop probably DXB.