Sarah, I'm really sorry for your loss. While, I can't say that I know what you're feeling, I can probably guess that they both would have wanted you not to be distraught by their deaths. I can almost fucking guarantee that they would have wanted you to have the fucking fantastic weekend you had.
I know it doesn't seem like you're in a good place right now but, it wasn't your fault and it's nothing you should be blaming yourself for. You're still an amazing person and you're still Sarah, the most you can do is to go to each of their funerals and attempt to express your love for your friends.
I really, and honesty love how much you dedicate yourself LW by still showing up, if your dedication to your friends is even half as strong as your dedication to this, I can really say is something to be celebrated for and something said about.
I would like to think that I know how amazing of a person you are but, I know that only a small portion of it can be transferred by keyboard. Your friends know the full amount of awesomeness you let them imbibe by your presence and would not want you to be this sad about it. Celebrate life and take things slowly, breathe and you can make this without feeling so... (for a lack of a better word) blank.
Sarah, you're a person of great worth and I know me saying it will mean nothing, but your friends I'm sure will fully agree with it. Feel better and go to sleep.
<3 Allen