Tenant brought a friend while touring the unit

[Anthony Salazar]

I am in the process of renting a studio unit on furnished finder. I'm in Southern California (Orange County) and I just showed the unit to a prospective tenant. He  (the prospective tenant) said he would be living alone but he also brought a coworker to look at the unit with him. I'm skeptical that the coworker might be more than just a coworker and that she may be looking to move in as well. She mentioned she lived near by and would stop by occasionally to hang out, but wouldn't be moving in.

I'm going to send him (the guy wanting to rent the unit) my application and I'm wondering how you would go about the coworker situation? The unit can allow for two people but I obviously want to make sure I have her fill out the application and do my due-diligence if she's planning on moving in.