www.yoropen.co.uk
They do pens and pencils, they are not just for left handers, but work really well, as the end is lifted up higher than the body of the pen and you can see what you are writing as you write it and your hand doesn't cover it up. You can also buy them in large branches of W H Smith.
Relax and try not to grip/hold the pen too tight, get her to hold a pen in her usual grip, then make sure that you can pull it out of her hand easily, if you have to pull hard, she is holding it too tight. Get her to imagine it is as light as a feather.
If she presses really hard on the paper, it means that writing can't flow, this is really important for doing joined up writing.
If she is pressing too hard, put some carbon paper (yes it does still exist) between two peices of paper and then you can show her the difference between pressing hard and pressing lightly.
Is she doing joined up writing yet? Is she forming all of her letters in the correct way and doing the correct type of joiner?
7 is young, but in my experience if it is a real problem, it won't just go away. Practise does make a difference to handwriting.