"Vent" accounts like this are a terrible idea. If you're in the public eye then yes, a lot of people will be critical of everything you do, some of them will be unreasonably petty and others will be needlessly antagonistic, but we really don't need a live feed of how that makes you feel at any given moment. It's an unhealthy self-fulfilling cycle, since these tweets draw in further, more personal criticism, which leads to more tweets etc..
Miori's in a pretty good place with her work all things considered, she's respected for her music, and has a lot of contacts in the industry and a strong portfolio, and it's absolutely fucking retarded to jeopardise that by lifting the filter too much on an alternate twitter account. At first I wasn't sure what to make of Ember saying Miori had offered to be friends with her privately but not publicly, but the way she's broadcasting all her vulnerabilities to randos like this suggests she's probably alienated most of her other friends by pulling that shit too.