How does she plan on playing her ranger at 80? If she goes with druid, make yourself a warrior or something along those lines. If she plans on being a dps, try maybe a mesmer tank or even an elementalist. I've got a ranger and an mesmer that I play with my boyfriend who has an elementalist that he is using as a healer because he enjoys the game play of the healing elementalist. We do well together.
Also if you guys are new and just leveling now I wouldn't worry about it too much. Since you can't use elite specs until max level, and you need to have purchased the related expansion to access them, there's no way you can make those decisions now. Just pick a profession that sounds good to you and you'll be fine running around and leveling.
You could do Reaper Necro, if you build even slightly tanky you are unstoppable and still pump out nasty damage. My Necro can take on pretty much anything solo.