If you’ve only been in flower for 5 weeks like you’re diary indicates - definitely no man it’s not too late. I’ve had purple strains hit in the last 10 days. Usually it’s like the last 2-3 weeks and flushing/ cold night time temps can help. But if it’s truly in her genes/phenotype - she’ll show ya some regardless of flush and cold temps.
I’ve noticed the super dark purples tho, you usually see signs within the first couple weeks of flower.