The obvious question to be asked here is as to whether the lady's computer has a DVD writer built into it. Otherwise, unless she's got a friend who can burn the disc for her, she'll need to buy an external DVD writer, such as this one:
https://tinyurl.com/n44y34b7
Then she simply needs some suitable burning software. While VLC, as recommended by Barry is a fantastic program, using it seems to be adding unnecessary complication to a very simple task. All that's needed (once a DVD writer is available, with a suitable blank DVD inserted into it) is to use Ashampoo Burning Studio Free:
https://www.ashampoo.com/uk/gbp/psr/7110/burning-software/burning-studio-free
Simply tell it that you want to burn a movie DVD, add the three relevant files to the file selection area and commence the burning process.
NB: While many DVD players can recognise and play DVDs that have been burned by a computer, not all can. So the lady would need to check that any DVD player she intended to play the disc in supports the type of disc that she uses to burn her Hollywood masterpiece.