The wass that yousee when you come in the door should be your accent wall. I live in a trailer and I had to make my end wall darker so it would make my living room look longer though

Phyllis,
I have heard it referenced as "cool" versus "warm".
Warm colors look best in North and East facing rooms, while cool colors lok best in South and West Facing rooms. (yeah, and don't ask me what you do in a SE facing room!)
I can attest that the cool sage I have in both the front and back of the house looks much better and truer in the SW room than in the NE room.
In your case, I think I'd put the accent wall on the plain wall, but I look forward to hearing the other responses.

I have a really large bedroom and I painted the wall that you see when you enter a navy blue.. Really pretty. It had been a sage green color. I also have a large living room. My daughter talked me into painting the one wall dark red. I was "not" sure about this. I ended up loving it. I have had so many compliments on it. The other walls are a taupe color. I really don't think there is any fast rule. I go with what I like and don't really worry about what others opinions are. Wouldn't it be boring if all our homes were alike?

Post pictures when you are finished. I'm sure it will be beautiful..

Are the windows themselves or the shades/blind/draperies pretty so that could be a focal point of the room when entering? Yes, even windows can stand out to be a focal point, depending on what's beyond them :) If it's the brick wall of the neighbors house, don't do the accent color there....

"Discover your ideal âÂÂspecial featureâ wall. Accent walls work best when there seems to be a logical reason why a particular wall invites special treatment, compared with other walls in the room. A dramatic architectural feature like a fireplace or an antique armoire may be good reasons to make a special wall stand out with color. Determine the âÂÂreasonâ why a wall might be painted with a standout color by asking a friend to enter your room and then quickly tell you which wall attracts her eye first. In most cases, the wall chosen will be the inherently âÂÂspecialâ wall in the room."

Is there space or does she have some pretty artwork, a furniture piece, to put in front of the accent color if she chooses the wall with the doorway?

In this house, there is a dark accent wall immediately on the left as you come into the foyer from the front door (decorator designed for the former owner, idea not mine). Plain wall, no window, door, nothing remarkable about it other than it's dark, and makes a great backdrop for a painting. The colors of a silk screened print that had been in our former bedroom was perfect for there.

To make the most impact, put it on the wall with no windows so that you can merchandise it with furniture, art and accessories.
What colors was she planning on using and what colors are her couch etc., drapes etc. I love decorating.