Help with my Chihuahua?

Hello everyone. I have a beautiful fawn coloured chihuahua, born in 2003. I have a problem with her though. She gets very congested, especially at night and battles terribly to breathe, then to get the extra oxygen she has obviously been deprived of, while she is battling to sleep she starts choking/coughing to get the air in. Dogs dont open their mouths to breathe, they only do that when they are hot, and pant to cool down. So its not like I can open her mouth to help her breathe, because she fights against me. Its very scary and what should I do? The vet said she might have to have her larynx enlarged etc, but I know she wont survive the anaesthetic. What do I do, is there a medication I can give her?