This could be described as self sabotaging behavior
Psychology Today describes this as:
What is Self-Sabotage?
Behavior is said to be self-sabotaging when it creates problems and interferes with long-standing goals. The most common self-sabotaging behaviors are procrastination, self-medication with drugs or alcohol, comfort eating, and forms of self-injury such as cutting. These acts may seem helpful in the moment, but they ultimately undermine us, especially when we engage in them repeatedly.
The person therefor might be described as a self-saboteur
More colloquially she might be described as her own worst enemy
He must fall either by his enemies, or by himself, who indeed is his own worst enemy.1
1 The life and letters of Marcus Tullius Cicero by By Marcus Tullius Cicero, William Heberden, Melmoth, Middleton; London, Henry G. Bohn, York Street, Covent Garden, MDCCCXLVIII