I honestly do not know whether my mum IBU or I am. Maybe some families find this familiar?
Growing up, my mum seemed to think that I spent all of my spare time screwing half the men in town. Even if I told Mum I was going to Friend A's, and gave her the phone number, she would never ring, but would accuse me of screwing half the men in town. It makes me feel sick to even think about it, the way I feel I was seen by my mum as having nothing more to offer in any liaison/relationship than sex. 
I know my mum felt she had little to offer but sex, from the things she's said over the years, things I don't want to hear really.
Anyway, now I have grown up, and have 2DC. My eldest DS has always been my mums favourite grandchild and she has spoilt him over the years to the point where she undermined me to gain favour with him. Now he is an adult, I have noticed more and more that my mother sometimes asks him things which I feel are inappropriate and she fawns over him. I cant describe it in any other way. If DS is home when she comes round, she will ignore everything I say and focus on him. Makes me feel like the least interesting person on the planet. She seems obsessed with him if I'm truthful. She then fires 1001 questions at him, because she has to know what he's doing at all times, and who he's going out with, and what he's going to wear out blah blah blah.
She cried for weeks when DS refused to move in with her when he went to uni, because she is 4 miles closer to the uni than I am. She kept saying how he had hurt her emotionally so deeply that she couldn't ever forgive him, and talked of how she'd never ask another man to move in with her again because men only ever hurt you. 
She spoke of him as if he were a partner. She rang all his friends, and asked them why he didn't want to be with her.
Anyhow, apart from all of that, which thankfully has died down for the most part now, she asks him what I feel are inappropriate questions, like 'What was your 1st sexual experience like?' DS goes red and mumbles 'dunno' and mum then probes further 'Are you still a virgin, I cant believe you're still a virgin, you must have gone so far with a girl by now, if i were younger I'd butter your toast in the morning'
When I intervene and usually say something like 'Jeez mum, even I dont ask him that, leave off, he doesn't want to talk about it' Mum just replys that she wants to know. WHY THOUGH
My mum also makes innuendos with me. She'll say 'why didnt you answer the phone earlier, did you have the rugby team round?' or 'In the summer, is it going to be hot and steamy in your house' to which I reply, depends what the temperature is outside.
Mum then says 'do you really not get it?' I say no i dont. I can tell by her voice that she truly thinks I have missed her point, then she spells it out to me in a patronising way.
If she knows a woman is in a relationship with a man and she cant work the realtionship out, if the man is younger, or the man is better paid, she always has to lower the tone to 'i know how she keeps him, she lays on her back, spreads her legs, screws him all day and night'
Make me feels so sick when she says this. Has anyone else got a parent like this? And why are they like this? What is the best way to handle this without falling out with my mum hopefully?
She seems to place so much of a womans worth on what she can do for a man, and yes, I have appallingly low self esteem and i struggle to understand why anyone, male or female would be interested in me as a person.