Whenever I decide to buy someone a knife, there are several questions I ask myself first before making a selection.
1. What are they likely to use it for?
2. Are they going to actually carry it, and if so, what type of carry method do they prefer?
3. Are they inclined to abuse a knife?
4. Are they prone to losing things?
5. What price range is appropriate for the individual?
6. What are the knife laws where the person lives?
Perhaps the OP has already answered these questions for herself. I know nothing about her boyfriend other than the fact that he has a thoughtful girlfriend.
A few things in particular I'm wondering about- if he is inclined to carry the knife, how would he carry it? What type of pants does he typically wear, jeans, slacks? Different types of pants react differently to the weight of different knives. Is he a "blue collar" guy, or does he work in an office? Is he someone who is comfortable going out in public with a knife clearly visible clipped to his pocket? Would it be legal to do so? Or is he is someone who would prefer something very discreet, like something small that could virtually disappear in the bottom of a pocket?
And when it comes to choosing a price range, I always think about all the times over the years I've seen people tell how they bought someone an expensive knife and it never gets used or carried, and when they ask the person why, the response is "It's too nice, I'm afraid of damaging it", or " It's so expensive, I'm afraid I'll lose it". If you buy someone an expensive knife to carry and use, but they won't because they are afraid of damaging or losing it, that kind of defeats the purpose of buying them that expensive knife in the first place.