Mara wears a red robe to cover up most of her body when she is out patching holes and fixing leaks in realities.

This is because of two reasons, one: she is self-concious of her obviously large and strange body and two: matter distribution and transfer of energy and information is different in her universe, i.e. she isn't used to the concept of light, and so only exposes one of her sensory organs at a time until she adjusts to it.

Her ear flaps make her look like an angel so she rolled with it and made it her branding and disguise. Most people assume her work to be a weird form of supernatural religious ministration and so don't bother her much about it.