quickchange123 Can I ask how old your little one is and how long she has been with you? Do you normally read out the letters? we do not read th eletters to our son (who is 5 and has been with us 18 months).
I drip feed in bits from the letters - e.g. I know your birth mum loves flowers, or liked fun fairs as a child, etc.
We did this for two reasons, one - we do not know of she will continue to write and two - we were not sure how much and what she would write.
If too long the letters might be met by boredom from ds, who is not that interested at the moment in his past. If the letters are too short he may be left wanting more! so drip feeding has worked for us.
I am not sure how I feel about a birth mum singing 'mummy'. Our son's birth mum signs her name. But to be honest for me, I am not sure it would worry me too much, he is my son, but his birth mum is his birth mum.
I feel her going on about how she feels is a sign she is not totally able to put his needs above hers. Which I understand. In your shoes I woudl try and teach my son to understand this, she is sad and misses you, because she loves you, but she could not look after you or keep you safe so there was no other way for things to be (I am talking about our situation, not yours).
You could ask social worker or contact person to ask her not to call herself mummy or not to speak about this or that. But she may not listen. I would be tempted to tell her positive stuff and try and guide her in what you would like to hear about, e.g. for me ds would like to know about his birth and when he lived in a house in the country etc (fake examples!!).
Good luck.