Women need not avoid vibrantly colored tattoos, and unicorn imagery is definitely the kind of subject matter that allows for many glorious hues.
Many scenarios would make for an impressive composition: a unicorn striding elegantly in a field, a unicorn rearing up to display power and emotion, or a winged unicorn soaring in a sky full of stars, its horn like a beacon, leading the way to a magical and ethereal world where anything is possible and dreams most definitely come true! There are many possibilities!
The unicorn could also be depicted interacting with a loved one, perhaps a young daughter/son gently stroking its nose or sitting on its back as it stands docile and reassuring.
Tattoos where the clients themselves are featured in the composition can often come off as more than a bit “cringey”, but if you lack that particular gene/restraint, and genuinely want to co-exist with a unicorn yourself, you could even be the one petting said creature or sitting on its back.
Riding a unicorn does sound really cool actually, and may be the only instance where such self-involvement is truly forgivable.
If you’d like to do something unexpected, however, do not overlook the ribald or raunchy: perhaps your unicorn is anatomically correct and sporting a second noticeable protrusion.
After all, where do baby unicorns come from? If it is a case of, “When a daddy unicorn and a mommy unicorn love each other very much, blah blah blah”, the daddy unicorn certainly needs to be “equipped”. If not, perhaps they’re simply born from rainbows? Truthfully, the latter does seem even more likely.