How many eighteen year-olds have met 'the one' at that age, even though they think they have?
I met the one at 18 at University - our education and careers did mean we had any years of a long distance relationship.
IL were initially nice - then as time went on and we didn't split increasingly less so. I was not what MIL wanted in a DIL - she wanted someone like her to go out with and she told me that often - she though DH should pick someone to suit her
.
FIL was fine till DH stopped falling in with them then I got blamed got worse when had children and found my backbone - then despite being married with kids they tried to split us up and told people this
. No effect and decade later they are back to being nice.
My parents very hostile to DH - as didn't want me having a boyfriend at all. Were like that till we got engaged many years after graduation - then decided they like him that stopped after marriage and first child came along - back to hostile. Then made few comments about us splitting.
All this has done is make us wary of them.
Nether of us compromised our education and career goals - we never asked the other to either. Different to my Dsis who made massive compromises and regrets them.
However my parents goals for me weren't mine - and DH goals haven't always coincided with his parents wishes.
It's possible GF could still adversely influence him - it's possible they'll split if/when he does go to University - it also possible they won't and she'll be around for years.
I'd spend less time worrying about GF - get him to focus on his long term ambitions - he'll need to work once at Cambridge as well as stick it out.
Also talk about how partners should encourage us and support us not dictated or limit our goals and ambitions - try dropping examples into conversations along those lines.
It's possible he does't fancy Cambridge university or even any university at all - and it's all him and not the GF at all. DH has had one student not work first year come and then say to him they'd never wanted to do University bit parents had insisted he try it- so he was dropping out been a pointless year all round.