fuming! advice please!

jas
So I'm 9 weeks pregnant. I told my boss 👂🏼I am a hairdresser and my boss owns the salon so there is nobody higher up that I can complain too👂🏼
last night as thought it was the right thing to do. I wasn't going to tell the other two girls I work with until 12 weeks into my pregnancy(they're both self employed) (I'm an employed apprentice) but when I told her last night she completely ignored me so I assumed she was going to speak to me in private when i saw her in work this morning! 
However she came in and completely blanked me, didn't even acknowledge that I was there. So I got on with my day as usual, I walked into the staff room at lunch time to find all 3 of them sat in there. For my boss to put me on the spot and say "so are you going to tell these two what you told me last night" (baring in mind they have only been working with us for a few months and I don't know them that well!) so obviously I told them. One of the girls said "that's so exciting" and my boss then turned and said 'stupid more like" (at this point I'm nearly in tears!!) I was then asked if I was keeping it to which I replied yes. 
My boss then went on to say "well I was clever enough to get rid of one when I was 19" (which is disgusting as she knows I lost a baby last September) which I politely ignored.. I then showed the girls my early 8 week scan picture and my boss took it off her and laughed then chucked it back to her! 
By now I've had enough, walked outside and burst into tears on the phone to my mum. This 48 year old women who I've built such a bond with over the past year has just made me feel small, humiliated and anxious.(I have anxiety as it is and being put on the spot and made digs at sent it through the roof!) 
So I'm asking advice on how I should approach her now? She didn't speak to me all afternoon afterwards, she's then told the two self employed girls that "if you want to know why I disagree so bad text me later' but she doesn't know I know that part. 
My mum wants to write her a letter explaining how unprofessional and hurtful she's been, but I don't want to make matters worse? 
Has anyone had a similar situation? I now don't want to go to work tomorrow because of how rubbish she has made me feel. 
Thank you for reading xx