I have a friend who wants me to make a bow tuck purse about 2-3" taller and wider than the ones I make (I use Penny Sturges ps008 pattern).

I'm pretty sure I know how to do this, just add the corresponding increases to the width and heights, but is there anything else I should be aware of before I start cutting the fabric she gave me and really mess things up.... Any suggestions will be totally appreciated!!

I think that's all you would have to do ... good luck! Show us a pic when you're done. :)

I enlarged the mini, to be 20 inches, so just go for it.
Turned out a great size for a baby diaper bag.

You might check to see if she wants the straps longer to carry on her sholder. I needed to lengthen mine about 3 inches to make comfortable for me.

Oh, I never thought of that, but that is a great idea! I'll ask her. Thanks!

I would make one first from a different fabric before I make hers

Working at a Elementary school I can see needing a larger bag. I would also use some different fabric for practice before cutting her. Good luck.