Should DD use JISA for uni fees or get Plan 5 student loan

[NotDonna]

DDs stocks & shares JISA has matured so it’s her money and her decision. It’s currently in a Vanguard life strategy ISA. I’m not sure either way so wondering what other people’s thoughts are please. She’s contemplating using it for uni fees rather than getting the student loan. She’s starting uni in Sept so would be on the new Plan 5 student loan with the following terms…

1. ‘interest’ added day one of degree at RPI which is currently capped at circa 7% atm (there’s no additional interest just RPI)
2. she will pay 9% of any gross income above 25k per annum
3. she will finish payments after 40 years or once full amount paid off
4. any government can change these terms retrospectively- nothing is concrete

Her argument is that…

1. 40 years is a long time not to expect change. Gov could start adding interest on top of the RPI rate for example.
2. the S&S isa isn’t performing brilliantly ie not above inflation or RPI in fact it’s been loosing recently. So she thinks the value will be less in a few years time than it is now so may as well use it before it’s worth less.

Her main worry is that governments can change the terms and I understand this. She’s trying to make an informed decision but there’s not much info out there. Even Martin Lewis isn’t certain about the whole ‘terms can change retrospectively’ bit!

The money doesn't have to stay in a JISA she could move it to a better performing ISA and the landscape changes.
Yes different loan deal, but DD moved to and adult ISA and the. Each tax year moves £4K into her LISA. Though we calculated in that she will be self employed so will always pay her student loan payments a year in arrears as they will come off through self assessment.

Doubt she’s got £150-300k lying about. She’d need to be a cash buyer to be able to buy.

It depends where she is going, there are still places with cheap housing. No she won't be buying in Oxford or London but there are other universities and towns close enough to commute.

https://springbokproperties.co.uk/properties-for-sale/under-50000?search=&filter-price-max=50000

AP5Diva said "The various blogs saying that “in real terms there is no interest” are deceptive bollocks because they’ve forgotten that the interest is compound interest, not simple interest. So the fact that the interest rate is at RPI % does not really, mathematically speaking actually mean you never pay more than what the money was worth when you borrowed it after adjusting for inflation- you pay more."
This is wrong. Both inflation and the interest are compounding, so it is arguably correct to say the interest rate in real terms is zero. Simple interest is rarely encountered in real life.
The problem is that we have at least 3 inflation measures and RPI is thought to overstate inflation.

I have been wondering aboutthis, there seem to be a lot of people generally recommending taking out a loan because so few people actually pay it off. Maybe that it is true if you are a very low earner but for anyone else I can see that you could still pay more than the initial amount even if you don’t pay whole amount once interest is factored in.

I guess maybe it depends on what she is studying or earnings expectations for the future but I’m be inclined to use the isa in year 1 at least.