You don't explain enough about what training your mare has in order to help you much, or about your level of experience, but it sounds to me that she is probably acting up more recently for two reasons. One, that she has grown into herself and is feeling good (and possibly full of grain,as tinyliny commented). Two, that the year of loving care you have given her has been too much love and not enough discipline. In any case, sending her away for training sounds positive. Make sure you follow up her training when she comes back home.