Donaghy was just 13 when she formed the band with Mutya Buena and Keisha Buchanan in 1998, but she left the group shortly after the trio found success in 2001 as she felt unable to cope with the pressure of fame.
The singer has reunited with Buena and Buchanan under the name Mutya Keisha Siobhan (Mks), and she feels more able to enjoy their second shot of success now she has grown up.
Donaghy, 29, tells BBC Radio 1's Newsbeat, "We started pretty young which obviously applied some pressure. We want to have fun and we felt like we didn't get the chance to enjoy it the first time around. Last time, we never did anything like that, the places we went and saw, it kind of goes over your head when you're a teenager."
Buena adds, "You don't appreciate it very much. You're too busy being insecure and a teenager, so now we are in our twenties and a little bit older and wiser, we can enjoy it."
Mks' new single Flatline debuted online last month (Jul13).