The copyright is a very grey legal area, but Venus clearly created the character "Venus Angelic" on her own at age 13. As she was a minor, it'll be impossible for either Margo OR Venus to definitively prove they own the material made when she was a minor and / or lived together. And that material is the only thing Margo can make a claim on; any material created in the past 2 months belongs to Fullscreen.
Regarding this claim - it seems that not only will YouTube take down a channel after the "3 strikes" rule happens (when you get 3 DMCA claims). After 4 days, the videos go back up and the revenue is then sent the the claimant / person who filed the takedown notice as the owner. Margo schemed until she found a way to get her hands on Venus's money once more.
But there's no way Fullscreen is going to kick back and watch their investment burn. Let's hope Venus has the wherewithal to push them for all the help they can give; she's not going to be able to this without a legal team, which she certainly can't afford.
If we have any US based legal persons in the house, feel free to weigh in; both Fullscreen and the YouTube servers are on US soil, which leaves this case under US jurisdiction for sure.