Light blond to red

My sister has very light blond colored hair. She used to have it colored deep auburn red years ago. She decided she wanted to go back deep red. She has turned her hair a deep pionkish red. She told me that she had put a neutral filler on her wet hair, left it for twenty minutes, dabbed it with a towel and proceeded to color. Her hair is in fair condition, however, I am not sure what to tell her to do. Should she fill it again or try another deeper color red???????

Any advise will do

Thank You for writing back. Yes, the filler had no color. Did she apply it right? She tried putting another darker red on it and the same thing happened. It all just rinses away.