You seem to be ignoring lots of advice from experienced guys on here and/or simply arguing with them.
I'm not going to chastise you for this or repeat their advice.
But coming from someone who once was in a LDR like yours, I'll tell you this...
If you remain in this relationship while both of you are in different countries, IT WILL END. You cannot sustain it.
Further, all that giddy fun sexy flirty **** you do when you see each other?? Much of that has to do with absence making the heart grow fonder. Since it's been a while between visits, you are both horny and hell and the romance again kicks into high gear.
Neither of you know what it's like to be around each other on a day-to-day basis. If I read correctly, you see her for about 5 days each summer? Really??? That's it? (apologies if I misread).
In my past LDR, when saw each other for about 2 1/2 months in the summer, 3 weeks in winter, and one week in spring. Yeah, in the shorter visits it was all fun, sex, etc. In the longer visits, occasional boredom and fights would happen. Once we had longer periods of time to be together we had to learn to live with each other 24/7. That's a different dynamic altogether than short little visits full of sex and travel and fun.
Anyway, for a LDR to be LTR, the problem is that you and her will not and cannot have the type of regular interaction required to really make an informed decision if you want to be in it for the long-term.
Since you are both starting uni and you say neither of you can move to be with the other, I don't foresee a very good chance of it lasting.
I may be wrong and you two will beat the odds, but I doubt it.
Now, maybe you didn't want to hear that. Well, here's something else you don't want to hear: Don't expect her to remain 100% loyal while she's waiting on you. Women love attention and, like us, they get horny. If she's an attractive women as you say, then d!ck is offered to her daily. If she hasn't already, she'll eventually take up a suitor on his offer. Heck, women do that all the time with guys they date and who live across the street. Across the Channel? Don't expect her to remain celibate for you and, for your sake, DON'T ASK.
Finally, my strongest advice you'll probably not take.... Do you REALLY, REALLY want to lock this woman down? You need her to move to where you are. That'll (1) show you her commitment for the longer-term and (2) push the relationship out of it's naturally devolving dynamic due to its long-distance nature. That said, if YOU MOVE TO HER, she'll dump you within the year, without a shadow of a doubt (she'll see it as weakness, you having no options, her having won the game, you being wrapped around her finger, etc.).
But you're young and that's when we learn, make mistakes, pick ourselves back up, grow, and so on.