I've recently unfollowed someone on Twitter, but she's still on a private list that I have. However, Twitter is still using her when suggesting tweets in the "Discover" tab.
Do I need to remove her from the list, or just wait a bit so that Twitter will update who to use in "Discover"?
Please consult http://support.twitter.com/
Specifically How to Use Twitter Lists
There are a few ways to create a new list, the easiest way is by clicking “New list” on the twitter sidebar. Clicking on this link will pop up a box, as shown above. Here you can name your list. You can also make the list public (everyone can see it) or private (only you can see it).
The homepage will always have the timeline of everyone you follow.
The profile page (twitter.com/username) will always have your tweets
The noisy users can be handled by this question
How can I throttle an over talkative person I'm following on Twitter without unfollowing?
Yes, it could either be that particular tweet is not part of a conversation (i.e No one replied to it or the tweet itself isn't a reply) or it maybe part of a conversation but the other person has protected their tweets.
EDIT
Protecting your Tweets
To protect your tweets Log in to Twitter and navigate to your Settings. Then scroll down and tick the check box Protect my tweets
Then click Save to confirm your changes.
Best Answer
I'm no longer getting tweets based on the person I unfollowed, even though I still have her on a private twitter list. It must have been a "wait a bit" scenario.