Rental Agreements: Landlord Pulled a Fast One

My question involves landlord-tenant law in the State of: Idaho

Background: I found an ad on Craigslist for a unit in a triplex. It advertised 6-month minimum lease, followed by month-to-month after that, which suited me just fine. I and my buddy were planning on moving out together to be closer to campus and work. I met with the agent a second time, and she gave me a draft copy of the lease to read over for a few days before I signed anything, which I thought was nice.

I read through the draft copy, made a few notes as to things we had discussed that weren't accurately reflected in the lease, and then went to meet with her again. Specifically, some questions on utilities and yard care. The draft agreement stated 6-months, followed by month to month after that, just as we had discussed. My buddy, who was going to be on the lease as another tenant was out of town, so they were going to meet at a different time and get his signature later.

When I met with her, I reviewed the draft copy with the true copy, and stated my concerns. It was slightly different than the draft copy, as she added clauses regarding pets, smoking, and visible storage, which weren't a problem. So, I signed the lease, and thus the adventure began.

The problem: It is now 3 days later, and I happened to glance at the rental agreement again as I was packing. Not only was it dated to start a month later than when I signed, it is signed as a year lease, not a 6-month. She changed it out in the true copy from the draft, her ad, and from what we had discussed in person.

Things that may help: My friend has not signed the lease yet, and I have told him not to until we get this problem settled. I have a copy of the ad stating 6-month minimum, as well as my co-tenant friend as a witness to her stating 6-month lease. As well, we haven't fully moved in yet. The copy of the lease I was given does not have my signature on it; only hers.

Potential issue: I think I still have the copy of the draft lease, but the move has been hectic, and I fear it may have gotten lost.

Questions: If the landlord is unwilling to revise the lease back to pre-agreed terms, do I have the grounds to get out of it? Is the lease still binding without my co-tenant (my friend's) signature?

Thanks!