Getting a BPD diagnosis takes much more than a suicide attempt and SI, because neither are exclusive to BPD.

Also, tattoos are not a form of SI, so all you actually have to go on is a Sui attempt, which could be straight up depression.

The other indicators you mention, I wonder about them, because this is such a personal diagnosis, its basis is on how we've (under)developed, our internal thought processes and how the ensuing behavioural reactions affects us and our relationships negatively.

So as a person with this dx, I wonder how someone (you) can make such an assumption (since you can't mindread) and what its actually based on...