When you are an introverted person from a subculture that encourages introverts, the low-energy state is not talking to other people about your feelings. That is the default -- not just as culturally imposed but as internally experienced. That is what you can do when you can't manage to do anything else. Extroverted people from cultures that encourage extroverts will often encourage us not to "keep it all bottled up," to "let our feelings out." So will extroverts who were raised in an introvert culture and have found other options. This is using the wrong metaphor. For a naturally extroverted person whose subculture has encouraged them to be an extrovert -- say, for an extroverted woman from the south -- it takes energy not to go, "Aaaaagh, this is driving me crazy, I am so frustrated, here are the things bothering me right now, aaaaagh!"
But that's not what's going on when you have an introvert from an introverted culture. If you treat us like we are really like you deep down and are inexplicably forcing ourselves not to be for weird cultural reasons, you will become confused, and your feelings will probably be hurt. "I thought we were really good friends," you will say to yourself. "Why didn't she know she could come cry on my shoulder? Why didn't she feel she could tell me how she's feeling about these things that were bothering her about her life right now? They're big things! They're upsetting things! Why would she bottle it up like that?"
Sometimes the answer is that you are really good friends, and she does know she can come cry on your shoulder, but she just didn't feel like doing that. Sometimes it's that she didn't feel like she had enough energy to do that. And that because you are such good friends she figured you would understand, once you knew the basic facts themselves, how she must be feeling. When someone's -- oh, gosh, I'm having trouble coming up with an example that's obviously close and yet not true of anyone specific on the friendslist at the moment -- anyway, when someone close to you dies, the other people close to you know that you are sad and upset. Or when there is a bad medical problem. Or a big relationship problem, or a big job problem. Or etc. Telling you about her feelings takes more energy than not telling you, and that may not be energy she has at that time.
This is all sounding like the Minnesotan way of saying, "Hey, I'm really not doing well," and I have to say that the last week has not gone well where the vertigo is concerned. Things have not been good. I have, for example, discovered that among mothers' least-favorite sentences over the phone is, "It really hardly counts as a burn; it's barely even there today." my habit of focusing on the good news is apparently not as reassuring as I'd hoped: "Neither the picture nor the vacuum cleaner was broken," in bright and cheerful tones, does not turn out to result in people going, "Oh, good! Glad to hear it! How nice for you then!" Sentences like, "Oh, I meant to tell you: both the gibbon and my uncle survived!" seem to strike me as more appropriate for leading into stories than they do other people. (People who have not conversed with me live and in person: be forewarned. I do this all the time.)
But mostly I've been thinking about this for other people, as a general idea. Not universally true of all introverts or all Minnesotans or at all times. Just -- something to consider. That when an introvert from an introvert-encouraging culture or subculture takes the time to talk about feelings with you, it may be because they are making an effort for your sake, because they know it's important to you, and not because letting it all out is what they really truly need. You may be letting it all out of the pressurized bottle. They are pulling it up from a well, bucket by bucket. And sometimes it's okay to sit down with them next to the well and just let them rest, put your hand on their shoulder and point out a funny-shaped cloud if you see one.