So, due to unchangeable travel plans, I cannot attend my cousin's wedding.  

She is quite upset about this (understandably) as I am likely her closest male family member.

Does anyone have any nice ideas for something I could do for her, or give her, to try and make her feel better about this?

something regarding her honey moon, like book her in a better hotel, or book her more days so she can spend more time in it. 

or give her your vgchartz account

Edit : i dont know why the fuck i qouted you when your the OP, sorry about that

Film a speech and get them to play it at the wedding as a surprise. I also agree with Bananaking, give her a nice gift for her honeymoon.

Burn down the venue her wedding is supposed to take place. She will be forced to postpone and relocate so you can attend then. Preferably some time after you get out of prison for arson.

you.... are.... in... an.. awful situation......

well, give her a chaning tatum clone....

This! Make it a surprise.

That way you'll be present in a way.

This is really a problem. You should put more effort with your gift. Maybe you should visit her and give your gift personally, a personal apology would be a great relief. Also, you can prepare a simple dinner for her, an event that will make her happy. I'm sure your absence will be forgotten. :D I agree that you can give her a couple trip!

tell her to cry you a river.

It is clear your travel plans were planned well before the wedding date.

If she was so close to you she would have checked if you were available before setting a date.

I'm really curious to know why the OP is going to jail.