Jennifer Coolidge, a blowsy rose of a character actress known for playing Stifler’s mother in “American Pie” and trophy wives in various Christopher Guest movies including “Best in Show,” is trying to adopt a plant-based lifestyle.

But it’s been slow going recently. Traveling to New York to promote a new movie, “Like a Boss,” she found herself flummoxed by airport and in-flight options. After a long day of interviews, with no good vegan options on the room service menu, she panic-ordered some fish.

“And I felt terrible,” said Ms. Coolidge, a ride-or-die animal lover and dog owner.

So on a damp Thursday this month, she made her way to Orchard Grocer, a vegan bodega and sandwich shop on the Lower East Side of Manhattan, in search of meatless treats.

“I’m having a hard time with the vegan thing,” Ms. Coolidge, 58, said, after she surreptitiously slid a half-eaten Snickers bar into a trash can.

Narrow and brightly lit, with ceiling-high shelves on one side, coolers on the other and a deli counter at the rear, the store was a curated vegan debauch: dairy-free chocolate, pizzas made with cashew cheese and rice-milk ice cream.

Ms. Coolidge, dressed in a camel-hair coat for which no actual camels had been harmed, a leopard-print minidress and black stockings, seemed overwhelmed.

A publicist introduced her to Nora Vargas, a bespectacled store manager with a forearm tattoo of an avocado and avocado-print shoes to match. “We’re not really healthy people here,” Ms. Vargas said. “We’re more into comfort food.”

Ms. Coolidge, an inimitable blend of girlish vulnerability, boss-lady poise and comic chops, was not opposed to comfort. “What’s your best thing here?” she said in her mellow, second-martini voice. “What do people go nuts over?”

Ms. Vargas talked her into a breakfast sandwich made with mung bean eggs on a butter-free croissant, and mentioned that a Beyond Burger, made from pea protein, was the daily special.

“I’m obsessed with the Beyond Burgers. Obsessed. I mean, I cannot eat enough,” Ms. Coolidge said, parting pink lips so bee stung that an EpiPen seemed like a useful accessory. “I feel like the Beyond Burger is orgasmic sometimes.”

As the orders went in, Ms. Coolidge sampled some mushroom jerky and popcorn flavored with yeast, which didn’t appeal. “I didn’t fart, I just opened this thing,” she said, as she handed the bag around.

She preferred Snacklins, faux pork rinds made from yuca, and a hazelnut chocolate bar from Vego. “Oh my God,” she said, adding 10 more Vego bars to the basket Ms. Vargas handed her.

When the sandwiches were ready, Ms. Coolidge cut them into quarters and headed outside to share them with her meat-eating publicists — a vegan seduction. “I’m trying to get everyone that I know to go this route,” she said.

But her publicists had disappeared. She gave the samples to her driver, seated in a black S.U.V. “We’re trying to convert people to the vegan way,” she said.

“I’m already a vegan,” he said, nibbling politely.

Ms. Coolidge flounced back into the store, where Ms. Vargas flourished a new treat: a whipped cream made from coconuts. A self-professed whipped cream enthusiast, Ms. Coolidge’s bedroom eyes went avid and wide. “Let’s try it,” she said, shaking the bottle with vigor. Before she could spray it right onto her fingers, Ms. Vargas brought over paper cups.

“This is delicious,” she said, her voice deepening to a purr. Ms. Vargas offered her a swirl of the store’s vanilla soft-serve ice cream, and Ms. Coolidge sprayed more whipped cream over the top.

“This couldn’t be any more fun,” Ms. Coolidge said. “People’s idea of vegan is, like, kale.”

Though she splits her time between Los Angeles and New Orleans, she has been contemplating a move to New York, where she lived and waitressed in the late 1980s and early 1990s. The soft serve confirmed it.

“I’m leaving L.A,” she said. “I’m single. I can’t live in a house on a hill and meet somebody. I need to come here and, like, be part of society.”

In “Like a Boss,” Ms. Coolidge plays a lonely beautician, Sydney, a downbeat riff on her “Legally Blonde” bend-and-snap turn. But in real life, even in Los Angeles, can Ms. Coolidge really not find a date?

Apparently. “I feel like a eunuch,” she said, as her black lace bra played peekaboo with her neckline. Men expect Stifler’s mother, but that isn’t who she is in her off hours. “I feel really like sort of a wallflower,” she said.

After spraying a third round of whipped cream onto her soft serve, she wandered next door to the grocery’s companion shop, Moo Shoes, to pet the store cats and try on some vegan footwear.

She went back and forth on a pink backpack, deciding it was too youthful (“I’m not fooling anybody, right?”), before trying on black high-heeled boots made of vegan leather and sustainably harvested beechwood. The boots didn’t fit quite right.

“Vegan girls have thin little feet,” she said, as “Hell Bent for Leather” by Judas Priest played in the background. Ms. Coolidge slipped her own boots back on and collected her groceries, plus a complimentary cat-printed tote.

“Come back and see us next time you’re in New York City,” Ms. Vargas said brightly.

“I’m sticking around,” Ms. Coolidge said, hefting her chocolate bars. “You’ll see me again this week.”