Мария пишите письмо на посольство. Вот Вам пример моего письма, который я всегда использую:
Dear Sir or Madam:
I am writing to you in support of a visa application for my mother Mrs ....... of ......(город), ......(страна), to visit myself Ms........ and my husband Mr......... in the United Kingdom.
I have enclosed as much documentation (pay slips, letters of employment etc) as I can to support Mrs ................ application

My husband and I will be providing all funds and accommodation for the duration of her visit. We currently reside at ..........(adres).
I trust everything is in order and that my mother Mrs .......... will be able come and visit my husband and myself.
If you have any further enquires please contact me at the address below or via email at ............(e-mail) phone: +44............. or work +44........
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