I, personally, second the scrapbook idea. The fact that you made it will mean so much to your friend. Not to mention, all the pictures are artistically arranged in one place for her to showcase on her coffee table. Frames, photo albums, and engraveable items are nice, but they're common and a little boring in my opinion. Anyone can go out and buy those things and you specifically said you wanted something nice and sentimental.
You can start your scrapbook with pictures of your friend and her hubby-to-be when they met and, like the other mom said, work your way through all the pre-wedding events. You can give it to her before the wedding and then tell her you will finish it out with wedding and honeymoon pictures. Don't waste time at those scrapbook stores, unless you need something very specific. Watch Hobby Lobby's weekly specials and go stock up on the items you want/need when they have their sales. Hobby Lobby usually has all that stuff at 30-50% off. Make sure you use all the acid-free paper, adhesive, and embellishments though...they keep your pictures from fading over time.