I couldn’t stop crying .. I needed counselling

in Manchester and I was so busy with interviews about leaving Coronation Street that I couldn’t get to see her so she was worried. She kept phoning to check in on me.”

Katie’s counsellor has suggested she write a farewell letter to Sinead or take a few days away. But she admits some of her upset could be connected to leaving her “Coronation Street family”.

“We’re all really close,” she says. “But I’m going to miss everyone. It’s such a life change.”

While she says she is starting to feel better, she reveals the role has also had an effect on her physical health.

She says she piled on a stone eating junk food and takeaways because she became so emotionally entrenched in Sinead. “The emotion involved in her dying meant I was just grabbing food and not really thinking about good nutrition,” she says.

“I was so tired when I got home that I’d order a takeaway. On set, there were a lot of chocolates, flapjacks and treats flying around.”

Coronation Street bosses offered Katie counselling while she was playing Sinead but she says it was only after leaving that she felt the toll.

“While I was playing Sinead, I was just so immersed I didn’t have time to focus on anything else,” she says. “It was upsetting at times, of course, but I didn’t think it was having any effect.”

The most devastating scenes showed Sinead recording a final goodbye message to baby son Bertie.

“The tears I shed then were real,” she says. “I put myself into the storyline as much as I could and it just felt so real. I imagined I really was Sinead and thought about how she’d really feel.

“I did that a lot with the role and I think that’s why it impacted me so much.”

She adds that soap co-stars Rob Mallard and Lisa George, who plays her aunt Beth, were also tearful during the last days of filming.

“We are really close friends and I think it was quite upsetting for them because it was not just Sinead’s last days but I was leaving too,” says Katie.

“The last few weeks were weird because every time we went into Sinead’s room there was an eerie atmosphere and everyone in the cast and crew would go quiet or tearful. It was like someone was actually dying.”

She tells how when she left she took a few of Sinead’s costumes home, saying: “Her pyjamas are so special to me. I feel close to her whenever I wear them.”

It was Katie who suggested to Corrie bosses her character should be killed off because a lot of shows cover cancer but few take it to the death.

She says she hopes Sinead’s plight will have a “Jade Goody effect”, which saw a huge surge in the number of young women going for smear tests after the death of the reality TV star.

Katie’s storyline has already led to women taking to social media calling for the cervical cancer screening age to be lowered below the age of 25.

She adds: “Nurses have messaged saying they have seen an increase in smear tests. It makes me so proud.”

Katie is also backing the Sunday Mirror’s mental health campaign Time to Change, to end discrimination against those suffering. “This is my first experience of mental health issues. It’s not been pleasant,” she says.

“My advice to anyone having problems is to get help as soon as you can.”

Now Katie is looking forward to some light relief – she is to play Tinker Bell in Peter Pan at Northwich Memorial Court this Christmas.

“I love drama, but my first love was comedy,” she says.