Reads really harsh because there is no sensuality at all, unless of course the hard-edged tone is what you're going for. it is all action, no feeling. This is really not a guy or a girl thing really. It is just the basics of showing vs telling. You tell us that the thoughts were making her hot. You tell us the actions. You tells us that she's fucked every way she liked. Telling doesn't put us in the moment. But you don't show feeling.
The mechanics of female masturbation is simple, watch Porn for details. Instead of fluffing a cock you are rubbing a clit or a sticking a finger inside. Worry less about anatomically correct descriptions.
Think about yourself and picture the feeling and sensations frame by frame.
You are in a bath. How does the water feel on your skin? What does the air feel like? Slow down to a standstill and describe the moment.
Your thoughts begin to wander. Naruto comes to mind. What first about him do you notice? The arms, what is about them draws your attention? "Big strong arms" is a bucket full of cliche. Do they glisten? Are the veins pumped around the muscles? How pink are they? Here you add sensuality. THe jaws? The lips that you imagine the wetness of his tongue. Does he lick them at you? Draw your eyes down his profile, the pecks and abs, and over to the groin.
Sexual feeling awakens. But what kickstarts it? The tingling the back your head? The heat pooling over your groin, that impels you to touch yourself? How does the water feel now? Describe the buildup of feeling moment by moment. Choice verbs and good adjectives go a long way. Stay away from cliche. If you resort to cliche, you aren't thinking hard enough or imagining hard enough.
You would find yourself thinking harder and sweating for the right words to capture the moment. Well, now you are writing with feeling.