5e tools, that'll help you with mechanics and items. If you want the books, DM me and I'll throw you a link to my drive where I got some of em stored, including the newest phb.

Though, you said she wanted something more modern. Maybe try CBR + PNK? The gist of it is, it's the character's last job. The character sheet fits on a pamphlet. If you want something a bit more detailed but still with ample room for mechanics, I'm reading through Savage Worlds and it looks superior to 5e in regards of speed of combat and roleplayability. Plus, there's loads of third party content to make the system fit pretty much any setting, including weird west (Deadlands), cyberpunk (there's a bunch of them), superheroes (i think it was called Capes, but I might be wrong), to fantasy (Paizo made a Pathfinder port to Savage Worlds).

As someone who just recently (1yr) started DM'ing, go for something simple. Don't drown yourself in options. And try not to homebrew too much. Go for a one-shot, but feel free to stretch it out to two or three sessions. You need any help, my DM's are open. 5e isn't as simple as some people say due to mistakes done by WotC and you need some elbow grease to buff it out as a DM.