假如你叫Mary，你的朋友Lily 到英国留学去了，但最近她写信说她不快乐，她学习很努力，但是英语还是不好；而且现在还生

One possible version:
Dear Lily,
I’m sorry to hear that you’re ill. Maybe the weather is quite different. Please look after yourself because nobody is there with you. If you are not feeling well for some days, I guess you should see a doctor.
I also feel sad that you are not happy in England because your English isn’t improving though you study hard. It doesn’t matter. Learning English well needs time and practice. If you work hard, I believe you can learn better.
You don’t like western food. I think you may try a little bit or go to Chinese restaurants sometimes. It’s good for us to enjoy different things. You tell me you miss the Chinese friends and we miss you too. Write to me soon.
Yours,
Mary

本文是一份书信，所以应注意书信的格式。要注意称呼，署名，正文等。
写给亲人、亲戚和关系密切的朋友时，用Dear或My dear再加上表示亲属关系的称呼或直称其名（这里指名字，不是姓氏）。例如：My dear father，Dear Tom
正文位置在下面称呼语隔一行，是信的核心部分。因此要求正文层次分明、简单易懂。和中文信不同的是，正文中一般不用Hello！结束语（1）写给家人、亲戚，用Your loving grandfather，Lovingly yours，Lovingly等； 2）写给熟人、朋友，用Yours cordially，Yours affectionately等；
（3）写业务信函用Truely yours（Yours truely），Faithfully yours（Yours faithfully）等；
（4）对上级、长辈用Yours obediently（Obediently yours），Yours respectfully（Respectfully yours）然后签自己的名字。最后还可以加上附言
正文可包括“你”向“她”的问候和建议。应该就题目中的要点提出建议。可运用in my opinion，as far as I’m concerned等高级词汇。可发挥想象提出建议。