It's not her ambition; it's her vices.
In Beckett's Jyhad Diary, several other vampires describe the current state of London prior to the Fall. One, Artie Basingstoke, describescalls her as "simultaneously arrogant and insecure." (p. 79) As the newly established Queen of London, she's using old tactics to deal with Sabbat and Anarchs — which in this case, includes the blood hunt. She's also secretly addicted to the act of diablerie (p.92) and is being set up for an overthrow that will put Mithras back in power.