I vote for throwing away the tennis racket!! No sense pushing a child into a sport that they don’t have any interest in. I think your child’s interest in foreign languages is great, but don’t just assume it is automatically her passion.
There is no right or wrong answer for ECs. If the child can’t show their PASSION for an EC, it is meaningless. They need stories for essays, for interviews, etc. that communicate why they felt drawn to tutoring immigrant students, or raising money for breast cancer by hosting bake sales, or spending hours inventing something that solves a unique problem.
You probably will never know WHY your child will get accepted/rejected by any particular college. And you will probably have both acceptances and rejections. How can the same kid be liked by some schools and rejected by others? Some of it will have to do with the volume of applications received by the college. And when a college is looking at 30,000 applications to fill 800 open freshman spots, you can see that whether your child played sports or volunteered at a homeless shelter seems less crucial a decision.
All you can do is encourage your child to learn HOW to study well, have them do their work as independently as possible (increasing independence with each passing year of high school) and giving them opportunities to interact with a variety of possible hobbies and interests. It could be an academic interest that leads to being on a team that goes to national competitions, or it could be a singular interest that goes deep and doesn’t win any awards. It could be the arts/drama/music that gets them excited.
Show your child that you love them no matter what. Give them the confidence that will allow them to venture out and try new things. Don’t assume that every new venture is “the one”. Let your child try something new without having to commit to doing it the rest of high school.
There are so many avenues to explore with an interest in foreign languages. D’s college roommate is going to be a medical missionary in a spanish speaking country. You can work towards a job in the State Department. You can travel the world as a translator. You can teach English classes in China. Now you won’t do those things as a high school student, but you can talk to people who work in those kinds of jobs, and you can find ways to volunteer at libraries or other organizations that read to children who don’t speak English. So many opportunities to pursue if your child is interested.
Use family outings as a time to discover things together. Take your child to a night of music/drama/theater, a museum exhibit, travel to interesting places, interact with older and younger folks who might enjoy the child’s company and brighten their day.
Just live life and let your child soak it all in. There will be some things they will keep coming back to, if you give them some freedom and some space to explore.