My first thought would be essentials as well, with a slayer build fighter being the most straightforward option. In my mind it has the following advantages:
1). Striker damage through largely static bonuses. This will allow her to feel effective while simplifying the math and not to have to be constantly asking which dice to roll (i.e. Rogue with intermittent sneak attack style.). I think a lot of new players are intimidated by slowing up the game, so this will mitigate that.
2). Striker tactics: easily the most straightforward of the game, it will keep her from constantly have to calculate burst radius, optimal positioning for her mark mechanic, or which of her two bloodied comrades to heal. Additionally, I find that strikers are often more forgiving of sub- optimal play, which will allow her to control her character, rather than being constantly told to" come over here and do x".
3). Defenderish armor and durability- you never want to make a newbie a glass cannon, its too stressful for them and those that want them to enjoy their first game.
These are just my two cents, but I recently started playing d&d again after a ten year hiatus, so am very newbie aware. I think essentials are definitely the way to go and all the characters I've made with them have been fun. Good gaming!
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