Fairies are spirits. That person is a human. Magick cannot change you physically in any way, shape, or form. Magick works within the confines of nature. It does not contradict physics or science. So though Fae are real, no you cannot become one. Only work with and honor them as you can any spirit or deity.
Magic is a force. An energy. Magic cannot change you appearence or being. I used to want to be a fairy, or a neko, or just a plain old animal, i tried magic. It never works. You can use Magic to summon something to you, as long as it exists and is a real thing, and the spell is a real spell. I dont really know, because im new about magic, but i think fairy tales, and mythical creatures, are more of a beleif than magic. Therefore, fairy schools are probably not real. Also, dont beleive everything you see on the internet. This website has tons of users who are real people who study real magic, and are humans, and always were humans. If you still want to study magic/wicca, continue use of this website. it could proove good. If you had enjoyed watching the youtube videos about "magic" keep watching them for enertainment. but dont have your deams crushed if they dont work. if you do keep watching them for entertainment only, Fairy Truths is a good channel even though its pretty much fake. I did see a pretty convuncing one where they showed there wings kind of growing on there backs, but they never actually showed them as real faries so.
Anyway, good luck with your magic!
The line between fantasy and reality can be a thin, curvy, hard to see one. But it is there. And, as has already been well said the idea of changing your physical form into something other than human falls on the fantasy side of things.
As to whether that means these people are lying outright, well, they are certainly mistaken anyways. it may be that they have lost their footing enough to believe what they are saying on some level, so they might not call what they are doing lying. Maybe pretending would be a better word? I suppose it depends on whether they are trying to actively mislead people, acting in satire, or if they are just making something meant to be entertaining within a world of its own to tell a story.
When talking about change and discovery on a Soul level, things can get a bit more malleable. Which is where one might start to encounter ideas like Therians and Otherkin. Which is a topic that tends to liven up any esoteric debate no matter where it happens to crop up. *anyways* When it comes to the Soul and its form, that can sometimes be a bit more malleable when looked at through a spiritual perspective.
First, the idea of reincarnation and soul growth over the course of multiple lifetimes, which is based on the enduring quality of consciousness from life to life and also even between lives. Then there is the idea that energy, consciousness, and soul can exist in multiple dimensions, and be connected with multiple different places in different ways. So it stands to logic, through those basic premises, that it is possible for a soul to incarnate as more than one species from time to time. As uncommon as it may be, there is nothing stopping a soul from incarnating to an entirely different world if it serves one's purposes at the time. or even simply spending time between lives on a different vibrational level or dimension, to gain learning and experiences that way as well. And then those experiences may in turn leave a personal impression that someone might end up connecting with later. For example through past life regression or meditation, or through plain old reconnecting with the Higher-Self.
There are some key points and differences between such a phenomenon though. One is a re-connection to what is already present as an influence of the past (otherkin). The other is a desire to change what you are now into something different and new, usually out of a desire to dis-associate with a current present life situation.
Using the Fairy example here, it is indeed possible for an individual to awaken into an idea that they might have spent time either living in a similar way to a fairy or some member of fairy-folk, or in a fairy-like place during a past incarnation elsewhere, or as time spent between lives in a particular astral/spiritual plane. However it is not possible that the same person would have the ability to make themselves into a fairy now, in this current physical life as a human.
Well that was a waste of 10 minutes doing some digging on that channel, I want that time back now.
All in all - its teenagers playing make believe to the point where they have started to believe that it is actually real. They have no real information on magic - at all.
Always take claims like that with a grain of salt. If someone claims to be a fairy or anything similar to that then be careful what you believe from their story.
'So are those girls on youtube lying about their experiences?' yes, yes they are. people can lie.
while there are people who work with faeries and believe they are real, they are not physically real. they're more like spirits, and can influence situations/people with their natural abilities, but they too have limits. a fae could bless/curse someone, but they cannot transform them. real magick works with nature, fae are seen as nature spirits, they [as well as magick] cannot contradict nature. [even magick has limits]
if you wish to work with faeries, the most you should spend your money on is a reputable book about a faerie magick path [ https://www.llewellyn.com/product.php?ean=9780875427331 might be of use] otherwise, you can research online, try to connect with them on your own and build your own path [start by making a faerie garden. big or small, it's kind of like an altar for the fae where they can stay, and you can leave offerings]