A friend is having no luck finding a commuting bike that sort of fits and won't kill her back. She is very athletic and light for her height .. 6'7" and a 40" barefoot inseam, so her trunk is comparatively short. Her arms are long.
The standard advice is a custom frame, but those are completely out of her budget. (one bike shop suggested Seven to build a frame ... I'm sure they'd do a fine job, but...)
Trek's get flamed here a lot it seems. BUT, Trek makes up to a 64cm frame on some models. Here's one with an alum frame and carbon seat stays/fork (although I don't like the wheelset for heavier riders it would probably be fine for starters.)
If budget is an issue Bikes direct has a few models that come in a 64cm frame.
If used is an option, ebay is a good bet. In the 70's and early 80's you could get 27" frames (~67-68cm). I think the trend toward double butted tube sets put an end to this: All the 27" frames I have seen used straight gauge tubing, mostly ChroMo, as usually only the higher end models had the option for the really big frames. I've seen several such bikes recently sold on ebay for $100-$150 range.
If you use the options on the left side of the ebay search, you can check boxes for frame size. Be sure to check the "unspecified" box as well as the two largest options....as many listings don't give the frame size in the data section. It is pretty easy to spot a tall frame in the photos, even thumbnails...focus on the headtube.
The good news is that many tall bike frames tend to have a too short top tube for folks with "normal" proportions. Us folks with long limbs and shorter torsos actually fit pretty well on them though.
PS: Don't have your friend PM me, cuz I don't like tall girls....Nope, not at all. Especially not red heads, or blondes, or brunettes. I like short ugly ones, preferably bald.
E-Bay often has "bargains" on super tall bikes. Some of them are custom bikes that sold new for thousands of dollars. But, there are very few bidders, due to the unusual size, and they often sell very, very, cheap.
Trek makes very tall sizes of some models of hybrids and mountain bikes, as well as road bikes. Your friend should visit two or three Trek dealers and get personally fitted. A high, but ultra-short stem will bring the bars back closer to the saddle. Obviously, the higher the bars, the shorter the distance between the saddle and the bars. So, when you get the bars up as high as the top of the saddle, the saddle to bar distance is at its minimum.