Donaghy formed the group with Mutya Buena and Keisha Buchanan in 1998 but the current lineup features none of these founding members.
Buena was replaced by Amelle Berrabah in 2005 and Jade Ewen took the place of Buchanan in September.
However, Range told BBC Newsbeat: "I don't want to sound like I'm being bigheaded but the Sugababes had one album which didn't sell and they were dropped.
"I joined eight years ago and we were signed together by Island records. I've been there since our first number one 'Freak Like Me' and been part of the history of the band ever since."
She added: "Amelle has been in the group for over four years and she's been part of our biggest album as a group. I think it's unfair.
"That's not disrespecting what previous members have brought to the group, but we were signed as Sugababes to Island Records and I'm still signed to Island records as Sugababes."