Background: I have a full time, quite stressful management role and also have a diagnosis for Generalised Anxiety Disorder, although this is now largely under control and I've been doing really well recently. I'm 25, no children and a lovely DP who I'm engaged to, but the wedding isn't until April 2018. We bought our house 2 years ago, I pay bills and mortgage as I'm the main earner and we couldn't afford the house if I lost me job, hence a lot of pressure for me which sparked the anxiety in the first place 
. DP works but doesn't earn a lot, he pays for our food and any treats we want. We are very comfortable with this arrangement and MIL know about how we split our money etc. All in all, not bad going for 25 and I'm very proud of myself and DP thus far.
MIL "popped round" last night and I was in the middle of painting WarHammer models, something I enjoy doing and helps me to relax because it's detailed work and requires concentration for extended periods of time. For those not in the know, WarHammer is basically tiny plastic models of fantasy creatures that you paint and then use to play a table top game. DP also paints Warhammer but to a lesser extent and prefers actually playing the game. It's something we do as a couple.
Anyway, MIL came in, spotted my epic dwarf army on the painting table in the living room and scoffed loudly, making "so childish" and "it's a kiddies activity" noises 
. She was actually sneering and looked utterly delighted that she'd found something to pick at. I ignored this and smiled my sweetest smile and explained how it helps me to relax, I find it enjoyable and it's something DP, myself and a group of our friends all do together.
She then went on to tell me how I should relax by planning the wedding and shouldn't have time to "sit about painting bits of plastic" and that I'm wasting time that I could be using for something productive... no mention what so ever to DP who also paints, has done since he was a kid and she knows this.
I didn't say anything, but I thought about it after and actually if it wasn't for me, her son would probably still be living at home aged 28 with no prospects, no house and would probably still be painting warhammer without me! It upset me because I genuinely don't think she realises just how hard I work to support myself and DP and how bloody much I need my time in the evening where I can zone out and just not think. I'm not hurting anyone, I'm not neglecting any other responsibilities so what the actual fuck is her problem??
I feel like whatever I do in life will never be good enough for her and I'll never be "right" for her son. This is not the first time she's been like this with me. More examples:
When we bought the house she came to look around and proclaimed it "too small and cold"... it was December and had been empty for 6 months . It was also the best we could afford.
I got a 1:1 at Uni and I was so bloody proud of myself.. but when DP told her she started calling me "billy bookworm" and went on and on about how Uni was about experiences and anyone who got a first must have been studying all the time and wasting it.
When I got my job she proclaimed it was too far away from home and I was going to "neglect" DP and there was no way we'd ever stay together long term... we've been together 9 years all together.
When we got engaged she asked DP "are you sure?" in ear shot of me...
WIBU to start distancing myself from her? She's really not good for my mental health.