First of all, if your friend is a she and you are a man... then please just let them walk their road and whether they divorce is none of your business... (sorry, no offend, but just want to say it first)
In fact, if she got marry for such a long time, most likely she has her own hk id already, she could come to hk and ask for legal assistant by government...
But if she did't got the HK ID, sorry, then she could only use the travel visa to hk and talk to her husband for all the arrangement... or check with the social department... as... she is semi-hk citizen already and their son is also a hk citizen... they are still protected by the law...