Definitely not her place and definitely neither your own problem nor responsibility.

Unfortunately I believe the only answer is to confront the woman about this. Ignoring it will only make this a mountain or a problem which will become harder and harder to break free from.

I don't envy you but I have in fact been in somewhat similar a position.

I was an acquaintance of a young woman as we were coworkers. On one occasion, having recently left my husband, she was very nice enough to invite me to a family holiday supper. My friend was graciously ensuring I was not alone for Easter. I then met all my friend's family including her mother. The woman immediately latched on to me and unfortunately we exchanged contact information.

Well my friend it turned out was (undiagnosed) depressed. I could tell this and I did my best to be a good cheerful friend. Her mother however felt it was my responsibility to make her daughter happy even to the point she would chastise me if she found out I did not call her daughter all the time or include her in my every activity. Well this all came to a boil on my friend's 30th birthday. Her mom practically ordered me to throw a surprise birthday extravaganza. The problem was, that at that time I lived near 1200km away! What a head-shaker. Honestly, just how on earth the women thought this way.

So I explained to her the predicament - which she knew full well I had moved. Her response was to demand I take time off and fly back to the City to organise and throw the party. She was counting on me to do so and really leaned on me with the guilt trip.

So I had to have a confrontation. It wasn't pretty but it was done. I told the woman I could not and would not do it. I also told her under no circumstances was she to contact me again. Boy did I catch an earful about what a horrible friend I was and that her daughter didn't matter to me.

That was nine years ago. I eventually did tell my friend about what her mother was doing behind her back. She was as you can expect absolutely mortified. She was completely unaware.

Thank goodness though the monkey was off my back - it only took me five years to do it.