Lucy Hatton says none of the athletes who changed allegiance on Tuesday will get "her spot" on Great Britain's team.
Kettering's Hatton, 20, won silver in February's European Indoor 60m hurdles, and over 100m has a qualifying time for the World Championships and Rio 2016.
But American-born and now Great Britain eligible Cindy Ofili has that mark too.
"I'm a British girl and I'll be on both teams. If you want to be GB we girls aren't going to roll over - bring it on," Hatton told BBC Radio Northampton.
|The four other 'new' Britons|
|High jumper Victoria Dronsfield from Sweden, Anguilla's Zharnel Hughes (100m and 200m) and Americans Shante Little (400m hurdles) and Montene Speight (400m) have all been declared eligible for Team GB too.|
"She's not taking my spot. Fair enough if she needs to come over because America's a bit too hard for her at the moment.
"But try and run in the wind, rain and cold because it's not as lovely as it seems."
British Athletics announced that five new athletes in total were now eligible to represent Britain.
The news was criticised by World Indoor 60m champion Richard Kilty, while former Olympic heptathlon bronze medallist Kelly Sotherton said she was "not sure about it".
Ofili is the younger sister of British 100m hurdles record holder Tiffany Porter, who made the same nationality switch five years ago.
Porter and Serita Solomon, who was beaten into third place in the European Indoor championships by Hatton in March, have also met the standard for Beijing this year and the Olympics in 2016.
A maximum of three athletes can be selected, with the British Championships in Birmingham from 3-5 July acting as a trial for the Worlds.
Hatton is the sixth fastest Briton of all time with 12.84 seconds - Ofili, ran a personal best of 12.60 in June.
"It's such a shock. I only found out a couple of days ago, so it's still kind of red hot," Hatton explained.
"But when the British trials come round, it's two sisters and they're going to be focusing on beating each other.
"I know tactically that Tiffany can't handle pressure and Cindy's probably never run in England before so I'll welcome her to Birmingham."