Telling an avoidant that I am an AP?

if you'd like to grow, do something different.
full disclosure of all your issues would not be nearly as conducive to an organic relationship as addressing your issues internally as they arise.

you're stepping into the AP/Da (assumed) dance willingly, expect a rough ride. you'll have lots of opportunity to observe yourself and choose constructive ways of dealing vs. destructive.
you can still learn from it. every encounter is an opportunity to see yourself more clearly.

in my opinion, less talking and more doing about the issues, and let this person unfold to you instead of making assumptions about who they are and what they are about.

Thanks a lot for your answers!

I also agree that it's too soon to talk about attachment theory with her, and I'm actually not planning to like I usually do. The challenge is that if I wish to mirror back the level of sharing she provided me, I need to talk about my past, which is very similar to hers (alcoholic dad etc). This in itself will lead to talking about how my past created anxiety in me, which is something I am still actively dealing with. She was very open about telling me about how she went for therapy, so again, if I want to mirror that back, I should tell her that I have seen/am seeing therapists. She told me quite a lot about the effects her past had on her sister, less so on herself.

So ideally, I'd like to have fun and just see what is possible. I've been doing pretty good so far I think. Like I said, I managed to keep my fears in check, probably because there have been less triggers in general (I feel very comfortable around her, therefore not activated) and because I managed not to unfairly project my doubts and fears on her the few times I became activated. I am trying something different for once, so I agree with juniper that full disclosure "would not be nearly as conducive to an organic relationship as addressing your issues internally as they arise." This is precisely what I am trying to achieve.
But yeah, so far the whole thing is giving me plenty opportunities to observe myself, choose and apply constructive ways of dealing, rather than destructive ones!

The part about not making assumptions is a bit more difficult. Now that I know by her own admission and looking at her past that she is very likely to be a DA (but again, few behavioural signs so far in the way she interacts with me), my fears are further activated. Ie abandonment fears (if she finds out I'm anxious like her sister, she might freak out and end things) and the overall knowledge that AP/DA relationships are rough even if things work out.
I am trying to give her the benefit of the doubt though, and see how she's like with me, before jumping to conclusions. Not so easy now after her disclosure.

Anyway, what I'm trying to say is that I can "fake" being secure all I want, but that I can't hide my past when someone asks about it (especially when there's been disclosure on the other side, this doesn't seem fair to hold back). How to make sense of my past (and present) in a positive light?

Being myself and honouring what I am sounds like good advice. It's actually what I've been feeling so far, expecting that she will do the same for me.
It's only know that I'm hitting a known wall. Most of biggest walls come very early on in relationships and things get easier with time.

It may sound like hard work because the most important work in my case has to be done in the beginning, when I am easily activated. As a relationship progresses, so does my sense of security.
Not sure about being ready for a long distance thing...but I like to work with the opportunities I have. I know that when I don't try to take them, I just stay home, alone and depressed.
I see it as a good opportunity to learn a few things, focus on the present, even if things don't work out.

I'm trying to look at it as an opportunity to grow, yes. But I can't fully eradicate the thought of associating failure of this relationship equating to something wrong with me. Or else I would already be secure, well adjusted, whatever. And most likely not on these forums! Having this much knowledge about attachment theory for people like us here on this board is a double-edged sword. It can be used as a tool to be wary of situations, but can quickly backfire if we rely too much on such abstract cues. I read in your comment both advice about not reading too much into things, and considering that she might be FA (why not!). To find out would mean spending more time reading into things/analysing situations, I think. Which is exactly when this type of knowledge can backfire.

Anyway, she's not displaying any tendency of anything with me so far. It's her past that I have been reading into, which I interpret as meaning that she is very likely to be DA (or FA).

Thank you!

Well, you know that in a way APs are also unavailable since we keep attaching to people who can't meet our needs fully, this way we won't have a real relationship.
I heard a few years ago when I was in the middle of a long distance thing that when a person is ready for a real relationship they immediately discard a long distance relationship UNLESS there are concrete and final plans for one of them to move. e.g.: you know she is about to start a job where you live very soon, contract signed, accommodation sorted out etc or vice versa.

I am all for exploring and knowing yourself, we can't really do this without other people to be our mirror but take great care with your heart and her heart.

I have been in 3 long distance relationships, one of them resulted in marriage (we were engaged before he moved) and from my experience it is based on illusion and wishful thinking. It is nice when you don't keep it serious, only as a holiday kind of connection.