Don't Get Overcomplicated
Anything in the 75-80 gallons range would be perfect for her. With some manufacturers that's a S boat, and with others that's a M (ie: the Karma M vs. the Burn M are ~16 gallons apart). I would go with a M size personally, because I like to float a little higher on lower volume runs. Past 80 gallons and she'd better be a fairly strong and competent paddler to throw it around, but if that were the case she'd probably not be asking for help during the selection process.
From your list I'd choose the Burn M or the Shiva M, but then again I'm partial to Pyranha boats over any others.
If you want to be the man, you've got to beat the man!