My 5yrs old does exactly the same. We restricted video games to only Saturdays so now he watches random people play video games on youtube all week. We're going to ban Youtube as well at least during the weekdays.
This is however hugely biased from having played a lot of video games as a kid and I felt it to be much more dynamic experience that may even help developing some mental faculties than passively watching anything.
In spite of all these exceptions what she wants to do most is hole herself off from her friends and family to consume her addiction fuel. If it were as easy as playing a video game with her, that would be wonderful.
I ask because you're primarily contrasting the solitary video watching that appears to be very important to your daughter with activities that involve others. You then emphasize the solitary nature of the activity with phrases like "hole herself off". It sounds like, in part, she might be seeking solitude.
I certainly won't deny that Youtube and others encourage habitual, compulsive, or addictive behaviors in the name of "engagement", but that may not be the only thing going on.
Watching YouTube videos is fine. Seeking solitude is fine. What defines addiction is not what your behavior is, it's whether or not the behavior is disrupting your life. So remarking that it sounds like she just wants to seek some solitude is irrelevant. It doesn't matter if she was "just" seeking some solitude or "just" using some drugs or "just" gambling or "just" shopping. It only matters whether those behaviors are disrupting her life. And I've made it clear that was the case by using language that includes the word addiction.
To explain why the "why" is so important... I know someone that does amphetamine about twice a day. They have real trouble if they go too long without taking any. When their supply starts to get low they will drop anything on their calendar to make sure they don't run out. They also have a prescription for adderall, which their doctor can only fill a month at a time, and when they miss a dose their diagnosis comes roaring back in and their intellectual performance collapses.
Alternatively... I assume you're at least relatively technical. When was the last time you fixed a bug without first trying to find a root cause for it? Even if you didn't find one, fixing a bug by patching over the symptoms, without ever figuring out why it was happening?
Anyway, for all that "she's clearly addicted" and "she has panic attacks if she doesn't watch enough youtube", you haven't posted a single mention of your daughter's thoughts or motives or reasons. You talk about her like she has no agency whatsoever. Mandatory minimum daily family time that just happens to be a nice round number of minutes, "it doesn't matter what the explanation is", comparing a desire for solitude to drugs, etc. I'm going to be completely honest, you haven't done a good job convincing me that her behaviors are even maladaptive.
What videos does she watch, why does she choose those videos, how does she choose them, and why did she decide on that method? Why does she think she chooses those videos? Can she explain her process for choosing those videos? Why does she think she enjoys those videos? How much youtube does she think she needs to be watching, how did she choose that amount, and why did she choose that amount that way? What would happen if she didn't watch enough youtube? Why does she dislike that outcome? Why does she think she dislikes that outcome? Are there any videos that're more important than others? Why does she think they're more important? Why does she value youtube over family time? Why does she think she values youtube over family time?
Our current position (which changes it seems every few weeks) is:
Rubbish stuff - 10 minutes per day - most youtube videos, especially vloggers in baseball caps doing Minecraft
TV - 20 minutes per day (exception because....as parents we both used to watch a fair bit of TV after school)
Worthy stuff - up to an hour a day - Nature documentaries - TED talks - youtube to research interesting things (currently Minecraft but only redstone)
I wouldn't wish enforcing this sort of regime on anyone.