Advise needed pls regarding food problems

Hi, my daughter is 14 and had her assessment in February with Paeds. He said she had all traits of ASD apart from she has good eye to eye contact and advance in using hands when talking. He said she needed to see psychologist before a formal diagnosis could be given and it’s a 6 month waiting list, but referred me to this website for help in meantime. 

I’d always had my worries as she’s grown up, but when she hit puberty 2 years ago it all came to the surface, I presume due to hormonal changes.

so far we seem to be handling things well, her eating atm though is driving me mad and I could do with some advice if possible please?

she’s always been a picky eater and preferred beige foods like chicken nuggets no chips etc… however as she’s gotten older and teenager she hardly likes anything which is causing a lot of problems at home. One min she likes something like mozzarella cheese toastie and 2 days later or a week later she’s gone off of it, I literally cannot keep up.

anyway it all came to a head tonight when I tried speaking to her about it as didn’t know what to make her for dinner and  she got abit mean and said she likes food in restaurants because a chef cooks it and I can’t cook anything nice and clearly don’t know how to use an oven…when I told her I was upset by wht she’d said she just said “sometimes the truth hurts mum”.

I have absolutely no idea what to do regarding her eating as even he doesn’t know what she wants to eat at home, the worst part is I’m not a bad cook at all, but I’m definitely not a trained chef and her will be. 

The way she s;oke to me wasn’t acceptable whatsoever and I tried to talk to her to explain why, but he said she didn’t understand what she had done so wrong and was just being truthful…how do I get her to understand??? 

she hasn’t been formally diagnosed yet and sometimes I feel so out of my depth and never know whether we’re actually handling things right or not?