Georgie
My mother is the same agem single and I can see this happening to her (yet, she doesn't have a house to sell, and only lives off an old age pension).
I'd approach it in a different way, if it was my mother in law. I'd sit her down and say, look, if you want to live in Bali for the rest of your life you need to look at say 20 or more years of income. You need health insurance, very expensive at your age, you need a regular income that will go up at the same rate as inflation (actually in Bali it is known to go up 3 times faster than inflation). So, lets do a long term plan for you to make sure you have enough, I don't think buying a place is a good idea so how about a 20 year lease on a place. Don't even mention the boyfriend just show support for her living out her years in Bali.
Even if Putu is a con artisit, he can stick it out for 20 years (many do) if he has a regualr income from her and a lease paid on a house.
I was getting blood work done on Monday and an expat older male was as well (his Indonesian wife was translating). The nurse asked him if he spoke Indonesian, he said no. The wife took over the conversation, the nurse asked how long he had lived here, wife said, long time, nearly 20 years, the nurse asked wife why he hasnt learnt Indonesian, the wife said, no way, I don't want him learning Indonesian then he can understand everything I say!
My nurse said to me: ha ha, if husbanad knows Indonesian then wife can't play him.... 3rd nurse in the room laughed and nodded at me, it was like all us woman were in on a dirty little secret.
I guess its fine, husband knows no better so will live a happy life with his happy wife.