This is my sentence:
1) In his letter, written between the 22nd and 28th of October 1885, I. D. Wilson mentioned Mrs. Beard who had promised to take care of the old Mrs. Wilson if she came to enjoy with her son that wonderful creation of the young architect.
2) ... if she would come ...
3) ... had she come / if she had come ...
I am not sure especially about that "if she came". I do not know if it is the right choice. I have thought of two other alternatives (2 and 3) but I am also unsure about them.
What is the right form of the sentence?