OK that's reassuring to know! I've done some more research since I made my post yesterday and there is a lot of people saying the same about female syrians, lots of testimonies about them being perfectly friendly and even affectionate with their owner and they'll still spend all of their free-roam time trying to bite through the walls/door.
I think Milkshake might also have been in heat yesterday because she seems a lot calmer today, happy to just sit and eat oats out of my hand rather than trying madly to escape.
I'll try not to let it alarm me too much then, just keep an eye on it and consider a cage upgrade if it gets worse