You could try a change in position to
I'm one of those unlucky girls where 99.98% of the time I need clitoral stimulation before I can achieve any type of orgasm. What I have found effective is me on top sitting almost vertical - from that position she can easily reach to stimulate her own clitoris while she rides you, practically masturbation without a dildo and you're free to lay back and enjoy the view
. Also leaves you with your hands free to do whatever else you like.
Problems you might have with this are:
1) If you're much larger then average and she's tighter this could be uncomfortable for her as the penetration is quite deep
2) If it is purely about mental stress on her part ( and that does happen) then this probably won't help at all, personally I would try this one only after you've had some success with
ASU2003s idea.
Another idea is once she's a bit more at ease (once again after
ASU2003s idea) you could try a shaft ring with an attached clitoral stimulator ( these can always be turned around to effect you as well btw) or warming / cooling gels or if you're feeling generous something like a wevibe (though if she needs large amounts of clitoral simulation she's still need to use some form of manual manipulation for the best results.
****
As for the sadness, my guess is that she probably feels terrible for not being able to orgasm with you. One because she's terrified you're going to start thinking she doesn't love you or doesn't find you attractive ( I'm certain that's not the issue). Plus if you get her close she'll be left with sexual tension all the time and feel even worse because she can't get frustrated with you about that sicne it's not your fault.
Massive guilt trip either way which just builds the original problems up and makes it worse.
Not much you can do there cept hug her, tell her you love her / care about her and you're not upset about the situation but will do your best to help her work on it.