I added arrow weight and brace hieght. Draw legnth has been there. The huntersfriend site seems more like a catalog. The only info I could get there was a comparison chart. So maybe I need to re phrase the question. My kid has a 23.5" draw legnth, her arrow is 280.8 grains, brace heigth is 6.5 and bow has twin cams. How fast do you think an arrow with that wieght should be moving before it could be considered an effective speed for hunting? I started with a 40lb bow 20+years ago surely todays bows are much more effective than back then. I know that shot placement will be number 1 concern.
To answer the bottom line on your question, somewhere in the 235fps range should suffice. This is simply based upon the info you have, and the chart on the lower listed Huntersfriend link and using the Bowhunting Safari KE calculator.
Here are a couple of links that you might can use, to help you get a ball park idea of the energy or your daughters rig.
http://www.sonoranbowhunting.com/calc.htm
http://utopiaprogramming.com/ke/KineticEnergy.html#
http://www.bowhuntingsafari.com/html/kinetic_energy_calculator.htm
Also I know you said it seemed useless, but here is a useful article that should help out when you find the actual speed your dealing with,
http://www.huntersfriend.com/2007-Carbon-Arrows/arrow-selection-guide5.htm
I am not sure if this was the one you referred to or not.
For the calculators, I like the last calculator because it will allow you to put in the KE your wanting, and the weight you have and it will give you the speed necessary to get it. This makes it pretty easy to set the bow up for a range by simply adjusting the pull to get the desired velocity with the chosen arrow. For the most part, generally speaking, if your pushing somewhere in the 45-50 range on KE with a good cut on contact head your in business, provided she can get the shot placement in the boiler room.
Try to get some arrows across a chronograph so you have the speed. Until you get that your simply guessing. Once you get the speed, try to get in the 35-40lb range and you should be good. I would not try using anything mechanical as they take away energy and momentum that she is already working to build up. You also might be able to squeek up the weight of the arrow a bit by going with a 100gr head, and get more downrange punch with out having to add too much speed to it. If they will still shoot accurately it is definitely worth the try. There are numerous 100gr COC heads that should work for her.
My friends wife is in a similar situation. She is shooting 40# with a 25 1/2" draw. We started her out using the Magnus heads. However, after getting a bent point on several we changed over to some of the shorter thicker bladed heads. She is getting full two side penetration, but not complete pass through. In other words not sticking the arrow in the ground behind the animal. The best heads we have used so far are Razor Tricks, CE-XT 4-Blade, Eastman Firstcut XT 100, Magnus Stingers 2 blade.
I hope this helps, I know how frustrating it can get trying to get the details down on things like this. Try to get her out on some hogs. If she can get through them, deer will not be an issue other than hitting where she aims. Good luck to the both of you, and remember, placement over all else will seize the day.