Hopefully they're well written because Sony isn't going to care about a few fan letters. If anything, it'll just thrive Sony to keep her even more than they already do. The more famous and relevant she becomes, the bigger the demand from competing labels to sign her (if the company was to nullify her contract). The best thing to do is support her financially.
Support her on social media, make sure everyone's aware that she has fans, and if and when she is able to record again and finally releases music, support her that way. Sony will have no choice but to promote her. They want MONEY, that's all.