We have something similar to this as well...
She writes Finnish, and when she does not know the Finnish word, she adds a English word in it. And when she does not know the English words either, she writes Chinese Pinyin. So often her sentences are made up of three languages. With a huge amount of typos and grammar mistakes. But after a while I got used to it and can almost always guess what she is trying to say.
But because of she is using bad Finnish and bad English... After I learned her vocabulary I started to use the same words that she understands. And explain things with her vocabulary... So sometimes when I speak English with some other friends, they are stunned how quickly my English has gotten from so good, to so bad haha...
Same with my mother tongue Finnish language. Even at work, I notice that I sometimes sound like an immigrant or something. But because of this the immigrants have no problems to understand me and my basic Finnish without grammar... Kind of funny but also very annoying. And she also hopes that I could correct her mistakes and grammar mistakes. But for some reason I just understand her and miss all the mistakes and miss all the corrections.