So, let's say I'd know somepony who I think is a unicorn who was born without a horn, she still is able to use magic to some degree but she clearly struggles! Is there something, anything that could help? I mean, theoretically speaking!
Well, first of all it’s arguable whether you can be a unicorn without a horn. In the literal sense you are not one, though that isn’t necessarily the determining factor, there are also social and cultural aspects, though that is semantics.
If for argument’s sake you are a unicorn without a horn, you cannot use magic in the sense we typically refer to magic within a unicorn context, i.e. casting spells. Friendship is of course still possible, which as we know is magic, so that would be an option.
Assuming we are referring to use of spells, a horn is required and there is no way around that. One would have to assume horns are optional in your hypothetical scenario, in which case there are so many assumptions made that you may as well be writing fiction.
Now, that’s not to say there’s no value in speculating, but if enough known elements are removed, the possibilities become so many one cannot draw any conclusions (concluding is after all about narrowing down possibilities).
In this instance, if fundamental knowledge does not apply, then I have no basis upon which to formulate advice, as I would have no insight into the mechanics at work. I could at best offer general advice I would give anypony, such as studying and practicing more, but nothing pertinent to the specifics of the situation.
