One suggestion is to get a drawing / writing board with the handwriting lines on it, like this one:
http://www.amazon.com/dp/B002SFLAQ8/Ruled paper would work as well, but my son preferred using an erasable surface. The lines may help your child self-correct sizing or relative displacement types of errors.
With regard to correct shape and sequence of the writing strokes, you can find on the web some guides like this one:
http://www.handwritingforkids.com/handwrite/manuscript/alphabets/images/tguide123.gifThere are different ideas about the correct sequence of strokes for some of the letters, so you should look at a few before deciding.
IIRC there are some Kumon workbooks out there that may help. We have some (can't find them at the moment) that were good for letter formation: there would be a heavy outline to trace over, then a light one, then you would be expected to write the letter(s) on your own.
One way I've handled this (having a highly independent kid myself) is to overcome any resistance, over time, to help/teaching. Incentives can help, and so can communicating clearly the benefit you can give. You may have to be highly persistent, depending on how set in her ways she is. This will be a useful life skill, being able to learn from others.
