Nothing wrong with inviting friends over to sit, chat and dinner
mah. I'm 23 and I have girls 14~16 coming to my house every now and
then and into my room alone with me loh... it's
clear that your mum doesn't trust you. Just a question: you the
only son?
Honestly, you yourself know that both of you didn't do anything
(yet), but you admit that
you have some sexual desire for her. So are you feeling guilty
towards your mum? Since now that you can't "make your move" or
you'll disappoint your mum even further as she already expressed
her "worries". But if you confirm that NOTHING will ever happen,
then why are you taking it into heart?
My advice to you is not to put too much into this "relationship".
As a friend, no problem. But if you wanna move further, just don't
but too much emotion into it. She may be lonely and wants some
company. Or she may geniuenly treat you as a friend. I don't know.
But just remember where the line is.