I married a woman and she lived with me for a while, then I divorced her and she married another man after me. She is asking whether it is permissible for her to meet my father after I divorced her, and to greet him with salaam.

Praise
be to Allah.

There is nothing
wrong with that, because Allah says (interpretation of the meaning):
“Forbidden
to you (for marriage) are: … The wives of your sons who (spring) from
your own loins,”
[an-Nisa’ 4:23].
They are the wives of the sons, so if the son divorces her, she is still a
mahram to his father. 

The mahram
connection between her and his father remains in effect. That is similar to
the case of the father’s wife; if the father divorces her, she is still a
mahram to the son. Allah, may He be exulted, says (interpretation of the
meaning): “And
marry not women whom your fathers married”
[an-Nisa’ 4:22].
If his father divorces her, she remains a mahram to his sons. The same
applies to the wives of sons. End quote. 

Shaykh ‘Abd
al-‘Azeez ibn Baaz (may Allah have mercy on him).