1- You can speak to her occasionally if everything you say is appropriate and professional (nothing haram is said).
2- However, if you cannot get married any time soon (and it would years away before you would get married), then I don’t recommend staying in touch with her because usually staying in touch with her ends up taking an emotional toll on you both. You will get more attached to each other and it would be painful to be away from each other. Also, sometimes this leads to frustration and it happens with some teenagers that after a while (like more than a year or 2 years) they start losing interest in each other and even hate each other.