A lot of the replies to the tweet share this sentiment, and it's starting to get annoying.
If she signed away the intellectual property to the company when she joined, it's theirs. It doesn't matter if it existed prior to her joining; she effectively sold it to them. Sure, it'd earn them some goodwill if they hand it back to the talent when they graduate, but not holding IP as leverage to ensure a return on investments could risk setting a damaging precedent for them if future talents just want to take the corpo for a ride. They have no moral or legal obligation to give or sell assets that they own fair and square to someone who is leaving their company.
vReverie obviously seems like a shitshow but there's a growing number of people who've made being performatively mad at vtuber corporations a significant part of their personality, and I don't care to let them keep moving the goalposts to shame perfectly normal business arrangements. They already sperg out at Phase for holding on to Yuri's character post-termination, and they're going to continue getting louder and more obnoxious as they find new holes to pick in other corpos.