A friend of mine wanted to get into League, and she said that her playing style is 'Staying back, going in, and then staying further back' or just 'staying back and sniping'. I'm thinking about possibly Jhin because she likes to stay back and snipe, or maybe Xerath, but I'm not quite sure. Any suggestions?
Trídent3 votesSnipers: 
(prob strongest/most simple long sniper one)
(longest range) 
(<--best matches for the style)
(really goes in)
(Geometry and lazers everywhere)or
Long Ranged: 
(Q) 
(<---can be far away in an actual teamfight out of the adcs) 
(Q spam) 
(R spam)
Others:
(super high skill floor/cap)
There's just so many possibilities DDD:
japan hate acc2 votesOk thanks so much!
Trídent3 votesNp, added a few more for your friend to chose from also
japan hate acc1 votesGreat!
Chaos Milk Tea2 votesChamps who can fight at range and suddenly go in
Champs who can siege from the backline like a boss
be warned, these champs are a bit difficult, but if she really likes one them they are worth learning.:
Best Valor NA1 votes Is exactly what you described.
ZED G0D1 votes Sounds perfect. there is NO reason for lux to ever be on the front line, except to proc her passive damage on marked targets, other than that there is no legit reason for lux to be even 600 units from the enemy. she can essentially artillery bomb them from a safe distance, and if they get to close just root them with Q and run back.