The group are a five piece dance troupe from The Wirral, made up of best friends Alice (17), Poppy (14), Julia (15), Annie (17) and Rebecca (16).
Speaking to the panel before their audition, Julia revealed she has Scoliosis and will soon undergo surgery which will leave her unable to dance.
"This is my last chance and I've always wanted to do it," she said.
Just Us turned MerseyGirls went on to perform to Rachel Platten's Fight Song.
After the routine, a teary Alesha Dixon said: "I have so much admiration for you girls right now, I can't tell you. Seeing how you come together, when you're passionate about something I can't imagine not being able to ever do that again.
"I really couldn't and that's why we all live, for the things we love to do. It really touched me."
She then hit the golden buzzer to send the group straight into the live shows this week.
Explaining the need to change their name, Alice said: “We do wish we could’ve stayed as Just Us but you have to stick to the rules.
“We were panicking a bit that people aren’t really going to know who we are – we’ll come on in the semis and they’ll be like ‘Who’s MerseyGirls?’ but at the same time, if they make it clear it doesn’t really matter at the end of the day.”
Julia told the Radio Times: “We went through loads – Inspire, Ignite, Limitless – and they were all taken by companies already. Then we finally settled on MerseyGirls. At first we were like ‘Oh, is MerseyGirls a bit cringey?’ and then we were like ‘Oh it’s OK, it’s like Jersery Boys!’”
Becky added: “We did like Just Us because it was our original name. But we do also like MerseyGirls – because we’re just five girls who like to dance who are from Merseyside!”
MerseyGirls compete in tonight's BGT 2017 final from 7:30PM on ITV.