This is right, you should learn how to draw in different styles, different techniques and more, after all it's all knowledge that you'll find a way how to incorporate into your own work. Or even more, allow you to have more than a single flavor. If she encourages you then I don't believe as others have claimed that your teacher is "classist" or that their advice is crap, or desperately wants you to stop drawing in anime style.
Teachers don't want an art student to get stuck into a single style at the point of becoming it a terrible bad habit that would later affect not only your artistic interests, your learning process but as well to negatively encourage your comfort zone. Teachers DO see potential in their students, that's why they want to encourage you to learn more and to don't stick to one single thing.
Consider it as if you were taking care of a toddler, you'd like the toddler to try a new yummy food right? Instead of them choosing the same 3 meals over and over and rejecting with utterly disgust to try something new maybe because it's red, it has a yellow sustance or because the "chicken" doesn't look like chiken.
As someone who has been in a High-School oriented to Visual Arts, attempted to become an art teacher (But due to times and distance I had to drop it), you need to know the following thing:
An artist that doesn't know how to do more than a single style, closes their chances of becoming a professional that can work in any field of their liking or in any field that requires someone to work, basically, if you need an art related job later, knowing to adapt to any kind of work that comes your way would be better than just accepting works based on what you like or that you know how to execute due to an over-fixation.
As well, when you're a student you'll have to learn even the things that you don't care about or that you don't like, different art styles, art movements are also part of it and you'll need to learn them even if you're gonna use them or not, just like Math or the approximate amount of red blood cells on our body.
Most of the time, as teenagers feel more accutely to what are being told to them, I want to make a mention that encouraging you to try something different doesn't mean you should stop doing what you like, nor that it's wrong, bad seen or it's unprofessional. Consciously, you know your teacher means well and as an educator, they want you to learn. But at the same time, keep in mind that emotionally, you'll think they are telling you to reject anime, when maybe it is not your teacher, but you yourself closing up to the idea without being conscious of it.
What you should ask yourself is what are you expecting to do once you finish school, where do you want to go, what do you want to do with your art, do you wanna live from it or keep it as a hobby, what kind of works related to your current abilities do you want to achieve, etc.
Not changing your style won't "ruin" your chances of becoming successful in the future, please avoid being overly dramatic. Not changing your style will only limit your abilities and slow down your learning process, as well, in some cases it will limit job opportunities. Not to mention, there are elements from other art movements/styles that you could incorporate into yours and to continue developing further more your style to make it more iconic or "original" as some may say.
