HO is known for giving out incorrect advice.
I stand to be corrected, but for dependents over 18, they still need to have a element of dependency on the main applicant and not be living an independent life. By marrying you, she is now your dependent, for 2 years already. See
319J(d) (click)
319J. Requirements for indefinite leave to remain
To qualify for indefinite leave to remain under this route, an applicant must meet the requirements listed below. If the applicant meets these requirements, indefinite leave to remain will be granted. If the applicant does not meet these requirements, the application will be refused.
Requirements:
(a) The applicant must not fall for refusal under the general grounds for refusal, and must not be an illegal entrant.
(b) The applicant must be the child of a parent who has, or is at the same time being granted, indefinite leave to remain as:
(i) a Relevant Points Based System Migrant, or
(ii) the partner of a Relevant Points Based System Migrant.
(c) The applicant must have, or have last been granted, leave as the child of or have been born in the United Kingdom to, the Points Based System Migrant, or the partner of a Points Based System migrant who is being granted indefinite leave to remain.
(d) The applicant must not be married or in a civil partnership, must not have formed an independent family unit, and must not be leading an independent life, and if he is over the age of 16 on the date the application is made, he must provide the specified documents and information in paragraph 319H-SD to show that this requirement is met.
