What can also make this confusing is that often, new members to an online community are urged to read over the former postings, to see what's already been discussed so they don't start new threads for ongoing discussions. Sometimes, it's even said straight out that if there is an ongoing discussion, new posts about it should go there instead of making a new thread...but then there ends up being an "unspoken rule" about how old that old thread can be before starting a new one is allowed.
And, of course, it kind of depends on the topics of the threads and the intent of a forum. If the thread is like most threads here, where the topic is "This specific poster is posting about a specific problem he or she is having and wants advice" then after a certain amount of time, the dead thread really should stay that way, unless the OP comes back. There is just no point.
But OTOH, if it's like some threads here in the sense that the topic is general and can be ongoing, then there is no reason why it can't be "brought back to life" if someone has a new idea. Such as, a thread about a movie title might get started: "What do you all think of movie XYZ", right when the movie comes out. Somebody doesn't get to see "Movie XYZ" until 6 months after the initial thread has stopped getting posts, but decides to read and post something anyway, and the discussion gets reopened. No problem there.
What's really concerning me about the newcomer in the OP, though, is not so much that she's navigating this difficult area, possibly with less than desirable results. It's the information in the update. I fear that that is what will make her difficult to deal with and I hope it all works out well.