The popstars, who form three-thirds of hit band The Saturdays, made the trip to the theme park on behalf of Mind charity.
Frankie, who has spoken publicly about her struggle with depression, became an ambassador for the organisation in January and launched the Prizeo Award - with a trip to the resort - to mark her support.
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"I'm going to be giving one of you and three of your friends the chance to come to one of my favourite places in the country, Alton Towers," she said earlier in the year.
"But, I'm a little bit of a wimp, so you're gonna have to persuade me to get on these rides!"
Perhaps luckily for Frankie, the pop star was unable to join in the rides due to her pregnancy. Sharing a snap of a "no pregnant women" symbol on her Instagram account, Frankie wrote: "managed to sum up my Alton Towers experience perfectly. In just one pic!"
"I was bag holder obviously!," she added.
Although Frankie couldn't make the most of the rides, she still had a great time: "Alton Towers fun," she tweeted.
Vanessa, who brought boyfriend Gary Salter along, added "Great time @altontowers with the gang today! All thanks to @MindCharity."
Mollie was also accompanied by her boyfriend, Jordan Omley, and the group enjoyed a cute photo together on one ride.
Frankie has openly supported Mind since she publicly announced her own struggle with depression in March last year.
Admitting her battle with negative thoughts and panic attacks since the age of 15, the singer announced that things had spiralled out of control.
"It set off this spiral of negative thinking – that if I disappeared, it wouldn’t matter to anyone. In fact, it would make everybody’s life easier. I felt that I was worthless, that I was ugly, that I didn’t deserve anything," she told Glamour.
Frankie spoke about the support she received from Mind upon becoming their youngest ever ambassador.
"I have got to know the charity over the last few months and am really pleased and proud to have been invited to be an ambassador," she said at the time.
"There is still so much stigma and fear around mental health and I hope that by being an ambassador for Mind I can help raise awareness and get people talking about something that affects one in four of us."