Will CrossFit cause bulky muscles? And can I prevent this?

Nothing like that happens overnight, particularly for women, especially not without performance-enhancing drugs.

Do genetics make some difference? Sure. Also relative youth, good nutrition, specifics of the exercise challenge, and more. Also, lean-ness (relative lack of body fat) matters. I know women who are remarkably muscular, even casually know some who've competed as bodybuilders. They look much more muscular when at low bodyweight, little subcutaneous fat layer, and right after a workout (pumped). Walking around in cute clothes, at weights above competition weight, not after a workout, they mostly look "toned".

Most important for someone like you is what I said first: Muscle gain doesn't happen overnight. It's slow. You don't wake up one morning and - poof! - bulky. You gradually get stronger, maybe eventually slowly add muscle . . . and when you reach a point you like, you stop pushing for gains, work instead to maintain the look you like.

For women, it tends to take a lot of time and work (without those PEDs, especially) to gain muscle mass. Personally, I wish it were easier to get bulky.

As Wolfman said, standard Crossfit tends not to be the most optimal method, if mass gain or a "bulky" look is what's desired.

And what if you do? You’ll be strong and beautiful. Muscles are damn sexier and more useful than a skinny waist or extra body fat.

I agree with everyone else, as a woman who put on a lot of muscle and who puts on muscle shockingly easily *for a woman*, even I would never worry about getting too bulky from normal exercise.

Even though it was relatively easy for me to gain muscle, it still took an enormous amount of work to gain what I did, and even then, I never looked too bulky.

Hell, even a lot of men have a hard time putting on enough muscle to look bulky. My husband diligently lifts weights every day and he's never been bulky.

If this woman looks bulky from large muscle mass she's some combo of insanely dedicated, genetically gifted in muscle development, taking steroids (MUCH more common among woman than people realize), or all of the above.

And even then, the dedication needed to get bulky for a woman, even with steroids, is massive. A lot of the trim, lean fitspo models you see are resorting to taking steroids just to be able to get those huge glutes that are in style that are otherwise quite difficult to build, that's how hard it is for many women to build muscle bulk.

So no, no woman in the world ever accidentally got too bulky unless she had a weird mutation like this muscle pigs. You don't need to worry about it.

Just enjoy your workout.