I like her thinking - just giving some thought it 90% of the way there really. So many don't plan or think about money at all.
I think given the cost of housing/renting, the 1/3 plan may be unrealistic. My son has got a graduate job starting soon as we're completely shocked re housing costs - a studio or small 1 bed flat will cost half his take home pay, and that's before power, rates, insurance, phone, etc, so it will be more like 2/3 just for living costs, and then maybe 1/6 for food & fun and 1/6 for savings!
We've talked at length with DS, not just recently, but going back a few years too, about finances etc so nothing is coming as a surprise. He'd been remarkably self-controlled with spending whilst at Uni, going to the supermarkets looking for yellow stickers, BOGOFs etc and restricting himself to 1 takeaway/meal out per week.
When he started Uni, we discussed student loans and we jointly made a spreadsheet showing the loan repayments, interest and length of time, based on different salary levels, so he wants to prioritise paying that off as he couldn't quite believe the amount of interest he'd have to pay!
Besides the spending/saving dilemma, just make sure she's building up her credit score/history. Make sure she gets a mobile phone contract in her own name, that she gets a credit card and uses it for small amounts paid off in full every month - get her on the electoral roll in her new flat, etc. Every little helps! Same with driving, get her on your own motor insurance as a named driver (assuming she doesn't have her own car already), so that she's building up at least some claim free history.
The other thing we've told our son is to sign up for whatever "offers" the employer is making available, such as discounted gym membership, discounted life insurance, full pension contributions, discounted private health insurance/dental insurance, etc - those "benefits" are usually very valuable, especially things like life, health & dental insurance which will cost more if taken out at an older age - they're usually dirt cheap if taken out when young, even more so with employer discounts!