Dear Alfresco,
Your mum is doing what most mums do 
getting
protective (or over-protective) of her son. She does Not want a
woman who doesn't measure up to her son, she only wants a woman who
deserves you to be with you. Some don't understand that by doing
this, they risk alienating the son forever, or ruining their
chances at happiness.
Since you've said that you only treat this lady as a friend,
perhaps your mum suspects that you're involved with her because you
bring her home. To mums, their sons only bring their gfs home,
perhaps? I don't know how often you bring your girl pals home, so
it's difficult to comment on this.
Lastly, your mum probably wants to protect you in case there's any
scandal brewing, like you're mistaken as the third party in this
lady's marriage. Have you spoken to her (calmly, I mean) about how
much her behavious is upsetting you?
FeowFeow
