Ebbie -

No known history with drugs

If is was her own, why would she take 4 kilos to Bali, where it is cheaper than at home?

Not sure how long whe was planning to stay, but I got the impression it was like a two week beach holiday - that sort of thing.

Yes, the ammount is one of many things that should have been queried at greater length. You don't take grass to Bali to sell. As someone else observed, that's like taking coal to Newcastle, and 4K or 9lb is enough to keep a heavy toker going for quite a while, or so I'm told.
Apart from anything else, a bag that size would have been as obvious as the beard on Father Christmas. She is clearly intelligent enough to know that.

There are many answers to question.