My mom and I are having a lot of struggle with my little sister. She is 12 years old and all of her life we have had a lot of trouble to try and get her into any activity at all. Currently she is in swimming and guitar. We are trying to expand the activities to karate and perhaps even a summer camp. She is throwing fits about not wanting to join anything else. She doesn't enjoy swimming all that much so we are trying to find something new. We got her to do a practice karate session and afterwards she cried and screamed about not wanting to join even though she had a good time. Any other sport or activity we suggest she immediately refuses and throws a temper tantrum. What can we do to help her want to join activities in a more positive manner? We don't want to argue with her every time for any activity anymore. Can anyone please help us?
This sounds like it could be some sort of social anxiety. The first thing I would recommend is not trying to force anything on her. Trying to get someone to overcome anxiety by force is trying to coax an animal out of hiding by shining a spotlight in their face.
I have dealt with social anxiety my whole life and the things that I was able to build up my confidence in while in a "safe" setting I can be very competitive and outgoing about. However, the things where I was dropped in and expected to perform I still don't do even though it has been over 20 years they were first pushed on me.
Try to incorporate as much variety into your family activities as you can and if you find something new that she enjoys, make time to do it with her more. If you can get her to open up about why she doesn't want to try new things it would help you figure out how to work with her instead of against her. Just don't put her on the spot and demand a straight answer, people with anxiety jump to the feeling of being interrogated very quickly. Social anxiety can be tricky to deal with as many people who have it feel they being judged at all times. Have patience and be willing to try things her way when possible.
Naturally, I can't say for sure if she has anxiety or not but what you described sounds very familiar.
Controlling the behaviors of others, especially adolescents and young adults, is a lot like nailing jello to the wall. So, your frustration (and question) is understandable.
Even when a change of behavior would benefit the person you're proposing it to, if they don't "feel like it", you can't force them into it... unless you have something they want more than their freedom.
So, if you're serious about her "need" to get involved outside of school, then start negotiating. There must be something she wants badly enough to take up an extracurricular activity for. Find out what it is, and see if you can afford to bargain with her in exchange for it.
If there's nothing, then I suggest you let her make the decision she feels is best for her. We are not all athletic, artistic, or extroverted; one size does not fit all.
I remember myself as a child and I thoroughly disliked going to almost all after school activities, even if I actually sort of enjoyed them when I went. I loved reading and would spend 4+ hours a day with a book if given the chance and if forced to go outside (which I was for my health) I would strongly prefer playing with friends or just making my own program over going to organized activities.
I come from a fairly strict household so it never occurred to me to actually resist too much when enrolled but unlike school, which I fairly enjoyed and certainly never ever skipped, I would skip all after school activities with regularity.
All together I don't think I lost much for taking this route and would strongly prefer not to force my child to have more extra-curricular activities unless she wanted to. Children have school to go to and unless there are some very strong reasons for wanting them watched over outside of school (behaviour issues pretty much) I feel they should get to manage their own free time within reasonable limits.
That doesn't mean I wouldn't encourage or offer possible activities, but I would try my best not to force.
She is likely to continue with that attitude as long she feels forced or pressured into doing these activities. A good trick to gain willing participation is to make it seem like it was her idea all along. Make an activity seem exciting without overtly suggesting that she participate. Highlight the benefits and potential. Dale Carnegie put it best, "Arouse in the other person an eager want." It should be an internal motivation, which you can assist to inspire.
For example, "Did you see that trick the figure skater just did? I could learn that move with some practice. I wonder if she is trying to become a professional. Imagine getting paid to ice skate as your day job! maybe even become an Olympian! Just learning to be that graceful would be enough for me...etc.
The first step in developing a passion is exposure. Removing the pressure and expectations may foster self motivation and eventually participation.