How can my friend in the US get travel document to attend wedding in Canada?

Hi, my friend wants to attend one of our friend's wedding ceremony in Canada. My friend is a permanent resident of the US but she does not have travel document. She needs it to attend the wedding ceremony in April. How can she get the travel document shortly? Please give me an advice. If necessary, how can we write a letter to the US immigration to issue her a travel document sooner? If you have samples, please share it with us. We do not want to miss her to attend our best friend wedding.
Thanks.

If she is travelling by air to canada she needs a passport. If she is crossing the border by ground all she needs is valid id with a picture. So guide yourself accordingly ... check with the u.s passport office and see how long it takes to get one.. seems to me she would have lots of time. If that is not an option she could fly to an american border city then travel by bus to canada or of course just travel by road to begin with

Don't write immigration, call them up and contact them directly about what she needs to leave the country without jepopardizing her standing for citizenship. Make sure you get all of the information from them confirmed in writing. If you find you are getting nowhere and need help contact your local congressman.

she needs to get a passport. YOu can get a passport application from any post office, Then once you fill it out you need to make an appointment at the post office in order to get it sent out. ( you need to give the post office your birth certificate also, because it gets mailed away with your application, (they will send it back), also , they will need two pictures, most postoffices will do this for a cost. Also, you need to take your drivers liscense with you to the post office. She needs to do this immediately, as getting a passport takes some time. ( I think like 2 months, and right now is a busy time for them)

Right along with Sden's answer,

that friend needs to get to the passport/registration office asap. If you have the invitation to the wedding with the dates, the length of stay & if they have already purchased their ticket to attend via plane, bus or train, then it might help to expedite the waiting & processing times & carry a copy of the invitation & the ticket.

Regardless of travelling by car or by plane, most Canadian customs are requesting the passport.