You can never tell her kid how to behave, she knows better that is why she had the kid, NO matter how correct, or right you are, It is her way and she knows better. Seen this to many times, years later I ask how is your Adult child, They try to avoid the conversation.
I met single moms that are straight, LGBT , that don't have real work, are Nosy, also Bossy and make Trump look normal, they only seek $$$.
In the old day before 1990, marrying one (single mom/dad) would last forever. But if you try that now or the person is born after 1980, forget it. It's all about $$$. Anyone born in the 70's is a grey area.
Look at ZOOM, that place is a psychological fest pool of deceit. But if you are good at reading people you will see the lies quickly.