Firstly, you've spelled 'vortices' incorrectly, which may make a big difference in a university examination.
The winglets have absolutely no effect on the vorticies.
I don't think this is entirely correct.
According to a Boeing publication:
The winglets increase the spread of the vortices along the TE, creating more lift at the wingtips.
All in all, I think FE Hoppy has the most astute answer to your query.