When she visits New York, Christina Applegate usually enjoys a welcome break from the Hollywood flashbulbs.

“No one ever looks at me or bothers me there, because I never wear make-up and I’ve always looked really dirty. This,” says the Anchorman actress, gesturing to her impeccable hair and make-up, “is an illusion!”

On her most recent visit, however, billboards and posters for Applegate’s latest film, Vacation, were plastered all over the Big Apple – much to the consternation of her four-year-old daughter, Sadie.

“We’d be on the subway and she’d be like, ‘There’s mama, again!’ It was very bizarre for her,” says the star.

“She knows I’m an actress, but she doesn’t quite understand what that means.”

Young Sadie won’t be settling down to watch her mum on screen in Vacation, which also stars Hangover actor Ed Helms and Australian heart-throb Chris Hemsworth, any time soon.

The film has a 15 rating in the UK, and Applegate says her daughter will need to be “32” before she sees it.

“I don’t want her to see Mommy say those things,” she says with a sigh. “Oh man...”

Vacation is the latest instalment in the rather bawdy National Lampoon’s Vacation series (other titles include 1989’s Christmas Vacation and 1985’s European Vacation), about the exploits of well-meaning patriarch Clark Griswold (Chevy Chase) and his family.

The 2015 reboot sees Clark’s now grown-up son Rusty (Helms) surprise his wife Debbie (Applegate) and their two sons with a road trip, to retrace the Griswold family’s 1983 cross-country journey to Walley World, a family fun park.

“As much as Debbie doesn’t want to do this trip, she does it because she loves this man, she sees his exuberance,” says Applegate, 43.

“She sees how much he wants it. And I think that’s what a relationship is – sometimes you have to sacrifice your own comfort to give someone else some joy.”

Rusty and Debbie’s marriage isn’t perfect, but Applegate, who is married to Dutch musician Martyn LeNoble, can relate to having to put the work in to keep a relationship strong.

“I think the key is, don’t try to change somebody. My husband and I, we talk all the time. It’s like, ‘I accept you for who you are and you accept me for who I am. I’m 43 years old, I’m not going to become someone different’. He’s the same way. ‘I’m 46, this is what you’ve got, you’ve known me for 25 years, you knew what you were getting into’,” she says.

“We’re like ships in the night half the time too – we have a four year old, I’m gone half the day driving her to gymnastics and play dates and school. Sometimes you have to check in [with each other]. And that’s what happening to Rusty and Debbie, they need to check in.”

As the only child of a single mother growing up in California, Applegate says money was often too tight for family holiday.

“We went to the Mexican border town Tijuana for a day once, my mom and I, in our Nova, that was it. We crossed the border, we went down the street, we brought a sombrero, we went home,” she recalls.

The actress, who admits she was “in the naughty kid group” in school, got her big break aged 16, when she landed the role of ditzy Kelly Bundy in family sitcom Married With Children.

She went on to appear in a number of films, including 2002’s The Sweetest Thing, alongside Cameron Diaz, and 2004’s hit comedy Anchorman: The Legend Of Ron Burgundy, playing news anchor Veronica Corningstone.

In 2008, aged 36, Applegate was diagnosed with breast cancer and decided to have a double mastectomy. She has since campaigned to raise awareness of the disease, and credited LeNoble with helping her cope. “Without him, I don’t know if I could have gone through any of it.”

Her family joined her during filming of upcoming low-budget indie flick Youth In Oregon (co-starring Billy Crudup and Frank Langella) in New York, where Sadie spotted all the posters of her mother.

The comedy is about a man who must drive his elderly father to be euthanised in Oregon.

“I don’t do not being with my family, so it was a family decision of, ‘Yeah, this has to happen’. We were going to go on a summer vacation [but] we uprooted the whole gang and went to New York City for three weeks,” says Applegate, who also has an 18-year-old stepdaughter with LeNoble.

“None of us made any money on that film. It’s one of these things you do because I needed to do that for my soul.

“The thing that gives me the most joy is being Sadie’s mother,” she adds, “so if you’re going to get me out of the house and get me to stop being her mother for a certain period of time, I’m going to make sure that if I’m going to leave her for 12 hours that day, that what I get to do is fun or inspiring or different or challenging for me.”

Vacation (15) opens in cinemas tomorrow.