I think that's a really nice question, so I'd like to help you a bit.
If you say she is a serious photographer, we have to define what that is. I'll help you with some Ringlight or Ringblitz applications.
The original intention of a ring flash was to photograph small objects that you really needed to get close to. With another type of illumination, the lens itself would produce strong shadows.
Some applications were close-ups of insects, flowers, coins, medical (as well as dental) forensics, etc.
So if she likes close-ups, we can discard some methods to get a ring light.
2. Urban look
I can not remember the first time I saw a ring flash for portraits. But as far as I can remember, Ringblitz gives you what I call "urban look." This is a strong emphasis on the person being shot, with little care in the background.
It creates an interesting shadow when there is a wall behind the subject or the main subject is simply heavily illuminated.
This is because the light decays in direct relation to the distance of the object from the lens. This does not occur with other light sources.
3. Catchlight and portrait
The previous point is more specific if you want to emphasize the catch light, and some people use dark glasses or close-up to see the catch lights on their eyes.
So. If you choose Door number 1, you probably want a ring flash that connects the light device to the lens and the power source to the hot shoe of the camera to connect the light with a cable.
Since the flash is attached to the lens, you will need the lens thread diameter, probably 52 or 58 mm. Most, however, have ring adapters for different diameters.
In addition, it is important to know the brand of the camera (in this case, Canon) because each brand has different pins for connecting a flash when using a TTL mode. There are also manual mode flashes.
The performance is not that great because you bring the light very close to your subject. They are small and do not "intimidate" your topic.
ON. ON LED-based Lens will be a good option.
Behind Door number 2There are a few options.
B. There are some strange looking ones softboxes where the whole box is held by the lens and you put in a normal flashlight. These are camera-dependent, since you can use any lens or camera brand. The softbox will not trigger a flash, but only defuse the light of a currently owned flash.
The main goal is not the catch light, which can be uneven, but the diffused light. They do not work for macros because they are bulky and block the view of the creative.
C. There are a few other more powerful dedicated ring flashes where you actually have a humorous flash tube. The light output is therefore higher than option A and B. If you use it too close to the person, you can hurt your eyes.
D. Behind Door number 3 You can use a ringlight independent of the camera. This is continuous lightand you just sneak behind it and shoot.
They are also based on LEDs, but have a larger diameter, so the catch light is notorious. Not so powerful that it can be next to the person and give the students time to close.
So … Choose a door to narrow your search.
P.S. Both can be for a serious photographer, but the options are a bit lens-specific.
There are different brands of softboxes. For example, it can be more serious that it has a solid construction and a truly cylindrical shape, with an amateur being a cheap copy that feels wobbly, for example.
Play a game and identify the types of ring lights:
But I agree with some comments. That kind of specific device … it's probably better to go to a store with her. But I hope you have a better idea now.