I thjnk transparency and honesty Is base line of marriage..y to let her go wrong if she only stumbling ..correct it right away not like Sherlock homes but like James bond..reinforce the importance of trust as the friend may or may not be wrong but u have to act right
can easily read the actions ..someone better has come in life and most likely he wants to quicken the divorce ..just sit and talk openly and make sure get alimony as per law
always remember once a cheater always a cheater ..these things are inbuilt and will repeat so dont think it will ever get ok..whether is with foreigner gf or local