how to apologise and advice

Well, if it's just a friendship, it should be a lot easier. Because she is making you feel this way and you have a bachelor's thesis, you should take a break until you do that, then go and celebrate it.

I mean if you're just friends, then you both should know and express you care for each other, and that you are not each other's priority (the ring is - if you guys are Frodo ad Sam ).

Why would you want to add to your friendship probably one of the only things from a romantic relationship that is troublesome. Because your problems do seem romantic relationship like. Or maybe the problem between guys and girls really is communication. Which I'm sure it's an issue a lot of the times.