hi need some advice for my mum who is travelling SIN > SYD > WLG
She was originally (all purchased on one ticket) on BA15 to SYD, and then BA7425 to WLG, but because of a delay inbound, she was moved to QF82 to SYD.
Some reason both the check-in and transfer desk in Changi only checked her bags thru to Sydney and told her she needs to grab her bags and get a new boarding pass in sydney.

Can she do this airside, or does she have to clear immigration and go thru again? just a bit worried since her original stopover went from 3.5hrs down to 2hrs and she's a bit slow.