A person is a person. Right now, Aspergers doesn't exist anymore in DSMV.
Yes, does sound like Asperger traints, but we can't do a diagnosis.

I used to have one-sided conversations about my obsessions to other people. If they showed one sign of being interested (which they may have done out of politeness), I finally felt safe to be uninhibited.

Does she have Aspergers or lack social skills? What is the difference? You say she doesn't get sarcasm and sometimes talks too much about one subject.
Well, that's what she does.
All you can do is politely nudge her into the right direction, or be more obvious with your normally subconscious queues. Like telling her you want to talk about something else now. Or ask her if she noticed that the person she was talking to was not interested in her conversation subject.

Don't interrupt her or call her out publically. Do it discretely.

Aspergers doesn't exist anymore. It's now called being high functioning while on the autism spectrum. And while it existed, there was no test to determine if someone had Aspergers or not. It was just the judgment of a single person, with professional training yes, but a single subjective judgment.