The worm's spell was strong, but her shield was stronger and his little curse bounced harmlessly away, exploding a section of the steps. His words brought cold fire to her veins and she decided she had had enough of indulging little Barty right now. There were bigger fish she wanted to fry up to sate her hunger. Barty would be the chips on her plate if he wasn't careful.
"And now I shall correct my mistakes by bringing about His glory again! You allowed yourself to be marked by someone else, child. You are worthy of His mark no longer! You will serve me to serve Him. You are not one of His chosen any longer!"
Bellatrix concentrated for barely a moment before she felt the connection to her own mark on the whelp. Shields couldn't block her will and her will at the moment was to make her supposed rival burn.