Fortification in team games...still don't get it.

Sorry, I'm sure this has been asked many times, but - I still don't understand how fortification works in chained team games. Here is a screenshot of my game (I am red, my teammate green):
When my teammate tries to fortify from Tripoli, Ghana is not a choice, while Kenya and Cameroon are. I assume they are options because they are adjacent to green countries, while Ghana is connected through several reds.
Therefore, fortification only works to chained own countries or teammate countries that are adjacent to any own country chained to the country I am fortifying from? Or is does the teammate country have to be adjacent to the country that I am fortifying from?

When my teammate tries to fortify from Tripoli, Ghana is not a choice, while Kenya and Cameroon are. I assume they are options because they are adjacent to green countries, while Ghana is connected through several reds.
Therefore, fortification only works to chained own countries or teammate countries that are adjacent to any own country chained to the country I am fortifying from? Or is does the teammate country have to be adjacent to the country that I am fortifying from?