OK, as has been said already. you are going to get biased opinions, so I'll try to not to.
I recommend she gets at a minimum a 3/4 ton with a diesel engine. I will not justify any particular brand, because that is up to her. My reasoning behind this is because they are set up for towing. Heavy duty brakes, heavy duty cooling, heavy duty transmissions, LT (light truck) tires, normally 8-10 ply.
The 1/2 tons may say they can pull 8-13klbs and yes they can, however they cannot do it safely and reliably. I can tow 100k but I can't stop it any time soon and most definitely not safely.
I have also learned the hard way, its better to get the big truck, because you will most likely upgrade the trailer sooner than you think and when you do you will have to upgrade the truck to pull what you want.
Also take into account, for every person that rides in the truck, takes away from the GCVRW, ie the size of the trailer you want to pull. The numbers they give you are for 1, 150lb person and no gear, trailer hitch or the other 3 people that weigh 200lbs each. Basically she will be much happier in the end with power needed to crest hills and get onto the freeway feeling safe. Also knowing she has the power to bring it to a stop without the White Knuckle experience.
So go big, and if she doesn't, at least warn others that she is on the highway driving dangerously so we can get off and get out harms way.