The best way to counteract the distracting behavior of Black Holes who lack confidence in their professional abilities is to take an active interest in their work. If you can build up their confidence, they'll stop looking to you for help all the time. Here's how to begin:
TAKE THE INITIATIVE.
Start the conversation yourself. Stop by the Black Hole's work station and talk about what she's doing. This way, the conversation is on your schedule, not hers. The sooner you take the initiative, the sooner she'll stop showing up in your doorway.
Each time she asks you to weigh in about her work, make a note of what stage the project is in. It's very possible that she may be stuck, waiting for the project to be explicitly or tacitly "approved," rather than moving on to the next stage of the project.
ENCOURAGE HER TO MOVE FORWARD.
Give her benchmarks (or, in the case of peers, suggest them) and clearly define how the work should progress. When you do this, you are giving the Black Hole permission to move forward - in anticipation of your approval. Then begin the conversation again from the top.
BRING HER INTO THE GROUP.
You don't want a Black Hole who lacks confidence in her social skills to feel isolated, especially if she is the keeper of important information or has contributions to make. Although you can't change her attitude about herself, you can affect how she acts at work. Start by praising her work and asking for her permission to share her work with others. You can do the show-and-tell yourself or have her do it. The fact that you are providing an opportunity for her to receive approval from her peers will boost the Black Hole's confidence.
Similarly, invite the Black Hole's input on the collaborative work that others do. Tell her publicly that her input and opinions are important. Give her increasingly visible positions based on her work, challenging her to top herself in presentations. She will feel safe knowing you are behind her. Draw her into interactions with others in groups. Remind her of her successful track record in public interaction as a means of encouraging more.
BUILD CONFIDENCE.
Encourage the Black Hole to have more confidence in her decision-making. Revise her job description, with her agreement, to include independent decision-making as part of the job. Schedule regular conversations to discuss her progress in this area.
Invite the Black Hole into your decision-making process: "I need your help making this decision." Then be sure to use her input and praise her publicly: "So-and-so and I made the decision." Black Holes frequently are talented people whose inpute will benefit you greatly. So facilitating their involvement is a win-win situation. Challenge the Black Hole to make increasingly bigger decisions.
Then, use specific vocabulary to support her decisions. "Good decision" is a powerful message. "I like that decision" also works. "That's going to produce exactly the results we need" is another opener.
Finally, document her increasingly responsible decision-making and remind her regularly of the progress she's making. Show her a map of how this work led to that work, which ultimately made the other thing possible, all as a result of her responsible decision-making. Don't let any good call go unrecognized.
None of this is to say that the Black Hole should become a major project and consume all your time. This is simply good leadership and a smart way to turn a difficult situation around for the better.
Your choice is clear: You can pro-actively and skillfully engage the Black Hole in the same way that you build up and encourage any subordinate, peer, or superior - or you can allow her to engage you on her terms, which will swallow up too much of your time and energy.