Sure, he she used Dhar directly (which is the only thing she can do now), but she has the theoretical framework to use Ulgu to pull off a Dhar dispel, At least that is my impression
@BoneyM can you clarify? Can Mathilde use the Second Secret without getting into the mindset to channel Dhar? If not can she atain this skill.
The mindset to channel Dhar takes you to a dark place. But so does the mindset to channel Shyish. The mindset to channel Aqshy gives you temper problems. The mindset to channel Ulgu gives you a flexible view of the truth and a hazy grasp of boundaries.
If Mathilde spends all her time channelling Dhar for a week, that'll put her in a messed-up headspace, just like if you spent a week researching serial killers or something. The Colleges teach Wizards how to ground their sense of self in companionship and small joys, the same way they teach them to ground rogue magic in copper and iron.