Avid Shakespeare buffs might already be familiar with Rosaline. She’s not technically in “Romeo and Juliet,” but her name is briefly mentioned in the Bard’s tragedy all the same as an early romantic interest of Romeo Montague. Remember the original lover he follows into a party thrown by his family’s notorious adversaries, the Capulets, only to be struck by the sight of her cousin Juliet? Charming and witty despite being tidily formulaic and a little too tame, Karen Maine’s “Rosaline” delightfully assumes the unsung cousin’s perspective in Renaissance Italy, invading the era with a contemporary tongue and attitude amplified by stringy covers of modern tunes like “All by Myself” and “This Will Be (An Everlasting Love).”

Considering countless modernized costume dramas and TV shows in the vein of “Bridgerton,” “Dickinson” and Lena Dunham’s nifty medieval coming-of-ager “Catherine Called Birdy” — not to mention iconic ’90s flicks like “Clueless” and “Cruel Intentions” that transposed classic texts to the present day — Maine’s likeminded outing might not render as instantly original. Still, her film succeeds at heartily seizing the timely idea at the core of those titles, displaying a feminist and feminine understanding of young women with desires, fears and preoccupations. Rebecca Serle introduced much of that in her 2013 YA novel “When You Were Mine,” which writers Michael H. Weber and Scott Neustadter (“The Spectacular Now”) have thoughtfully adapted, switching Serle’s contemporary setting back to Shakespeare’s original period.

But the film’s winsome disposition also owes largely to leading lady Kaitlyn Dever, who makes a feisty dish out of Rosaline’s sarcasm and independent personality with impeccable comic timing. Secretly canoodling with old-fashioned romantic Romeo (an affable Kyle Allen, sporting a purposely ridiculous Prince Charming bob) at the gardens and terraces of her family’s Verona estate, the headstrong Rosaline longs for a free and adventurous life outside family confines — not unlike Disney’s Princess Jasmine — refusing to be tied down with an arranged marriage. Serving eyerolls to the many septuagenarian suitors that her father Adrian (Bradley Whitford) lines up for her, Rosaline hopes to scare them off with crazy made-up stories, like having an imaginary friend that follows her everywhere. By her side is her closest confidante Janet (the great Minnie Driver), an accomplished caregiver who often and hilariously has to remind various skeptics of her credentials as a registered nurse.

Sure enough, the traditionally minded and attired Juliet (Isabela Merced) soon enters the picture, presenting a meek contrast to Rosaline’s unruly long locks and defiant demeanor. Her rebellious streak even extends to casually challenging her family on their stance against the Montagues. “If you hate them so much, why don’t you just move? I hear Siena is nice,” she suggests in one of her many outspoken moments. One wouldn’t expect such a go-getting fighter to give up on Romeo that easily, and Rosaline doesn’t disappoint. Determined to sneakily corrupt her cousin and break up her relationship with the guy, she assertively takes Juliet under her wing to convince her that Romeo might not be the only man out there. Complicating Rosaline’s ill-advised matchmaking scheme is Dario (a charismatic Sean Teale), a new suitor who might actually be a good match for our fiery heroine.

Charting these complicated escapades across vibrantly designed locations, Maine and cinematographer Laurie Rose opt for an undemanding visual style, letting Andrew McAlpine’s pretty, candy-colored sets and Mitchell Travers’ luscious costumes become the focus. Elsewhere, Spencer Stevenson and Nico Hiraga deliver memorable supporting performances as Rosaline’s bestie Paris and Steve the Courier, propelling our heroine’s tale to a satisfying climax that reimagines the fate Shakespeare determined for his star-crossed lovers.

There are shades of Jane Austen and rom-com staples such as “My Best Friend’s Wedding” in Rosaline’s pursuits, though Weber and Neustadter don’t necessarily take the story much further than that. What’s missing from the equation is a dose of cheeky salaciousness: One wishes “Rosaline” was as spicy in spirit as its protagonist, who is objectively better off without Romeo in her life. Still, there’s something fresh about the story’s unwillingness to pit a woman’s romantic quests against her career goals. Perhaps Rosaline can have it all, and become both a cartographer — her vocational ambition — and Dario’s lover as she wishes. Not necessarily for as long as they both shall live, but as long as her feral heart desires.