Summarize the following:
If you’re calling her or approaching her in person, you need to introduce yourself. While she might remember you, there is a good chance she might not remember your name. Take the opportunity to briefly introduce yourself. In addition, remind her of how you know each other.  Say something like “Hey, Ann! I’m John – we know each other through Andy.” Don’t be offended if she doesn’t know your name or forgets it later. Whatever way you decide to contact her, you should consider using humor. Humor will make a potentially awkward situation funny, and help remind her of your virtues. There are many ways you can do this:  Start with a light-hearted joke about something you might think is funny. For example, if you remember she really likes Oreo cookies, you can joke about those. Joke about fashion. For instance, say “I was just in the mall and saw someone that looks exactly like you wearing crocs.” Use self-deprecating humor. For example, say, “Hey, do you remember me? The guy who wears the absurd cowboy boots.” Contact her and start up a conversation about how she’s doing in life. If you’re interested in a romantic relationship with her, this is a good way to find out if she is available. In addition, this is a very honest and straightforward way of reinitiating contact.  Generally, you can say something like “It’s been a while since we spoke. How are you doing?” If you knew her from work, and one of you has moved on, ask her “So, what’s going on with work these days?” In the case you knew each other through a mutual friend, you could simply ask about whether she’s spoken to that person recently. While it may seem disingenuous, send her a text in which you’re talking to someone else, like a friend or a romantic interest. Make sure the text is simple, but somewhat intriguing. She may respond telling you that you’re texting the wrong person, or she might pretend to be the person you’re supposed to be texting. Whatever happens, use it as an opportunity to talk to her. You should eventually let her know that you knew that it was her you were texting or calling. Chances are, though, she will already know.

Summary:
Re-introduce yourself. Use humor. Ask her how she is doing. Pretend contacting her is a mistake.