Yip, if you don't want to see the womans comments/photos etc, then 'unfriend' her.
The letter is just nasty and cowardly. If these people were true friends, they would tolerate this new mums' pride and obvious joy for her new baby.
6 months old? My daughter is 29 years old and I am still proud of her; her wonderful Army career, her lovely husband and home, and her two beautiful sons.
Maybe this woman had difficultly conceiving her child, who knows? My daughter lost 3 babies before she had her two sons.
Don't judge. You never know what someone has been through and maybe they just don't want to say.