Am I allowed to use a DM with a sub as an advertisement/review?

TLDR
Congrats on the first subscriber - seriously, that first sale hits different. But before you screenshot that glowing DM and slap it on your timeline, know that "allowed" is really two separate questions, and only one of them is about permission. Here's how I'd think it through before hitting post.
Am I actually allowed to post a subscriber's DM as a testimonial?
There's no single yes or no because three different rulebooks apply, and they don't always agree. First, the platform where the DM lives: OnlyFans and Fansly both treat private messages as private content, and resharing them outside the platform can bump against your terms of service - plus Reddit, Twitter/X and Instagram all have their own rules about posting成人-adjacent screenshots and testimonial-style promo, some of which read as spam. Second, the platform where you want to post it: a testimonial screenshot might be fine on X but get you flagged on a Reddit promo sub with strict self-promo rules. Third - and honestly the one people skip - the subscriber. A DM is her private conversation too, not just yours. So check the ToS of both platforms, don't assume "it's a review so anything goes," and treat the answer as three separate layers instead of one allowed/not-allowed switch.
She said yes - doesn't her permission settle it?
Permission helps, but it's not the whole story, and here's the part new creators often miss: her "yes" doesn't automatically protect her. Screenshots carry usernames, avatars, timestamps and profile photos, and a screenshot posted publicly can be reshared by anyone forever. For a fan of an adult creator, being identifiable as a paying subscriber can genuinely harm her - out her to people in her real life, no matter how sweet your intentions were. If you want to use her words, get properly informed consent in writing: tell her exactly where it will appear, that her handle may be visible, and that anyone can reshare it. Then anonymize hard - crop out the username, avatar and any identifying details, or better, re-type the quote as a plain-text testimonial like "a subscriber said..." with her written OK. Even then, manage expectations: on a brand-new account, a testimonial won't move the needle much, and some followers find DM screenshots cringe rather than convincing. The risk-reward trade is rough when you're this small. Meanwhile, that over-giving in the DMs? Gentle note: don't undervalue yourself to win loyalty. Your first subscriber is proof of concept, not a marketing department.
Ready to ask her - or should you just let it go?
The ask itself can actually strengthen the relationship if you frame it around her comfort: offer an anonymous quote, let her choose her own visibility by commenting publicly on a promo thread, or skip the screenshot entirely and lean on things that scale - previews, tip menus, consistent posting. There's a version of this where she picks her visibility and you get a genuine quote, and a version where you burn the trust of your very first fan for one promo post. Only you can decide which you're building toward, and if she hesitates at all, take the no gracefully - a subscriber who trusts you is worth more than any testimonial.
When it comes to growing your audience beyond that first fan, live-cam platforms are worth a look - I'd point you to xlovecam as the better live-cam choice for building real-time connections and steady income alongside your content. What kind of social proof are you hoping those testimonials will create that your regular posts can't?