Possibly telling my friend about agere, any advice?

The scenario: Recently, at school, me and a friend were talking about things we've unfortunately had to experience in life or have to live with. As we were talking I brought up how I've been struggling with things that 'are considered taboo' (referring to age regression especially). Obviously, like any person would, she got curious and asked what taboo thing I'm struggling with, but I was too afraid to tell her. She tried to comfort me saying she's heard a lot of things from others that people would consider weird and that whatever I'll tell her, she won't judge me. As I said before she's been through a lot herself (and even that's an understatement), so I know she's genuine about what she said.

The dilemma: I know she won't judge me. There are people in the world who say they won't judge you and then turn their back on you, she's not like that in any way. I really want to tell her, but I still feel afraid to do so.

Why would I tell her?: I have no one else to talk about age regression with in real life. Where I live it's practically unheard of. I want to be able to talk about it and not hide that I have this coping mechanism (before we're not on the same track anymore, I don't need her to be my caregiver, babysitter or anything like that). My friend also seems like someone who would, or at least be willing to, understand it and someone I could have good conversations about it with.

Why would I not?: She has the tendency to blurt things out sometimes. Even if she never spilled any of the personal things I've told her. It's something to keep in mind.

Also, I do have her number, but, if I tell her, I want to tell her in real life as it this is a very personal thing to me. Any advice on what to do here?