To diagnose the condition leading to bilateral conductive deafness in a 30-year-old female wearing a hearing aid, let's analyze the possible options:

1. Presbycusis: This condition refers to age-related hearing loss, usually appearing after the age of 65 and is characterized by a bilateral sensorineural hearing loss. It typically does not cause conductive deafness, making this option unlikely.
2. Chronic suppurative otitis media (CSOM): CSOM can cause conductive hearing loss due to persistent ear infections and damage to the middle ear structures, but it is often accompanied by ear discharge. Moreover, it tends to affect one ear primarily and not commonly associated with young age as a primary cause of bilateral conductive deafness. Thus, it's less likely in this scenario.
3. Meniere's disease: This inner ear disorder typically causes sensorineural hearing loss, tinnitus, and vertigo. The hearing loss in Meniere's disease is usually fluctuating and sensorineural, not conductive, so it is not the correct diagnosis.
4. Otosclerosis: This condition involves abnormal bone remodeling in the middle ear, leading to fixation of the stapes bone, which causes conductive hearing loss. It is more common in young adults, particularly women, and often presents bilaterally. The use of a hearing aid is common for managing the conductive hearing loss associated with otosclerosis.

Given the age, gender, and type of hearing loss (bilateral conductive), Otosclerosis is the most probable diagnosis.