Oh, Pink, I so sympathise with you re your Mum. My Mum has always had food/diet issues too. She put me on a diet when I was 13 because I got to ten stone (I was almost the height I am now) because "ladies shouldn't be in double figures".
When I became anorexic at 17/18 she kept telling me how lovely I looked (!) and for years after I'd recovered she kept a photo of me at 6.5 stone in her wallet! When I got well again she kept telling me how ugly and fat I was. Great!
Not sure what to say to you except that you have to remember you are doing this for YOU. It doesn't matter what anyone says to you - only you have the power to succeed at this. You can choose not to listen to the naysayers. If you believe you can do it, you WILL do it!!
Would it help to listen to the negative voice, acknowledge it is there, but then tell yourself you will succeed anyway? I find it helps me to acknowledge negative/uncomfortable thoughts and feelings (because I used to always hide them by using food!!)
Just a thought.
For what it's worth though, you're doing brilliantly! (Jealous re the 30 BMI thing - I'm not quite there yet!!) Isn't LL great?!