It's difficult to say without seeing where the nail has lifted. I find if a client has a lifted nail then usually I can buff to remove all the lifted portion of the gel and then just reapply the gel thick enough to match the rest. But if she still has a tip on her nail and the lifting has affected that then sometimes I find it quicker to just cut the tip right down, remove the gel and start again with a new tip rather than waste time trying to save it!
Good luck x