One of the problems with anxiety, OP, is that it 'metastasizes' to other anxieties if you give in. If you were able to manage this at only photographing the door and the faucet, I'd say go for it. But don't let it go further. Don't then photograph the stove and your hair straightener so you can comfort yourself that they're off, too. I have anxieties, and found this advice very helpful. If you give in, pretty soon you'll be catering to your anxiety continuously.
She may be talking about the fact that your doing that just reinforces the obsession. What if the door was left unlocked? Intolerable? That's what ERP therapy does. It makes you get used to the idea of the unthinkable so that it doesn't bother you anymore. The pictures are an extension of the compulsion. The longer you do it, the longer the obsession keeps ahold of you. Since your mom is a therapist, talk to her about ERP therapy.
That's just giving in to your OCD. If you have rituals, in other words you actually have OCD instead of some of today's diagnoses that aren't actually what we used to think of as OCD, the treatment is to get into therapy and when you do you will learn relaxation techniques, get an understanding of the disease, and eventually you will be asked to not do your rituals and learn that not doing them won't result in any harm to you. That hopefully rewires your brain to stop needing to do the repetitive behaviors as you will have demystified them. If you take photos, you're just finding another way to do the rituals which reinforces the disease.