"My friend comes to my house."
Translation:मेरा दोस्त मेरे घर आता है ।
There is an implicit postposition before आता that corresponds to the word 'to' in the English sentence. मेरा दोस्त मेरे घर (को) आता है।
The object of this postposition is 'मेरे घर' which is why it is in the oblique case.
To see why this is the object, look for the part of the sentence that answers the question 'किस को?'/'To what?'. That would be मेरे घर/'my house'.
It agrees with 'friend'.
दोस्त is technically a masculine noun. This is why we use मेरा and the verb conjugates as आता.
However, there is no real feminine alternative for दोस्त. सहेली works for a female friend of a woman/girl but sounds odd for a female friend of a man/boy.
So, दोस्त is increasingly also used as a feminine noun too which would make the sentence 'मेरी दोस्त मेरे घर आती है'. This is technically not grammatically correct but common usage nonetheless.