You can play her support but she does far better mid lane. If you are playing normal matches it doesn’t matter.
The reason why is because she lacks many tools a support needs, high base damage on abilities, either hard CC or a heal/shield ability strong enough to make up for lack of hard Crowd control.
Orianna only has her ultimate ability to rely on for peel, and that has a high cooldown. That is not good when you need to consistently keep your adc alive. While you can shield them, you often need more than that, such as an ability like Janna tornado or lulu polymorph.
If your goal is to climb ranked try Janna or soraka.