Why hasn’t my ex of 7 years not told his mum we broke up still after 4 months?

She knows he is getting a mortgage on his own but she doesn’t know we broke up, his STEP family know but she’s his only real family - he tells me she knows but she doesn’t because she still answers my calls infront of him when I call to see how she is doing etc

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He says she knows we broke up, but she is saying that she doesn’t know anything, she asks me if we’re still together? Because she knows I haven’t been there in a while, I called her yesterday and he was In the same room as her cooking his dinner! But she still answered and said on the phone he’s cooking his dinner
Why hasn’t my ex of 7 years not told his mum we broke up still after 4 months?
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