Sorry to hear about your friend being unsupportive. I've also found a lot of people don't understand and are pretty ignorant about this type of thing and health issues in general actually. You can guarantee you're not alone in what you're experiencing, although you may feel it sometimes. It's great your mum is supportive.
I try to avoid going into detail on it with people (who often seem very curious) and tend to put it into words they identify with, lie if you have to! If people ask, I tend to say 'I have stomach problems and my doctor told me I have to avoid these foods'.. that type of thing, it's usually enough!
The diet may not seem manageable at the moment, but you'll be surprised how you adapt. It'll also become less important to you as you start to feel better from doing it. And you won't crave those foods as much as you do now.
I don't know where you are based, but most Western countries have a celiac/coeliac association--I've checked and France has a celiac society. They'll be able to tell you which restaurants specifically offer/cater to gluten free diets. See below link.
Ask them about restaurants, supermarkets, specialised health food shops.
You'll be fine in France. Like anywhere, with this diet, you will be safest (and easiest!) ordering meals without sauce--there are lots of nice things, especially in france, steak frites, grilled prawns and fish, vegetables, rice. Is all cheese out? When I was told I had celiac disease (no gluten), I was told to also avoid lactose for a while but hard cheeses like Gouda were fine. There are lots of non-gluten grains that you can have for breakfast--amaranth, corn, rice (don't have kellogg's corn flakes and rice krispies though--they may have traces of gluten in them), quinoa, buckwheat. Various gluten free grain crackers with different toppings.
I went on honeymoon last year to Italy, and it was fine. Allergies/special diets are no longer unusual, good restaurants are used to special requests.
For desserts, there's fruit or sorbet. For something more stodgy, how about rice pudding made with coconut milk, palm Sugar
and vanilla, when making pancakes you can use rice flour or another gluten free flour and substitute eggs with banana. Tapioca is another good one. There are options, it'll just take a bit of time to get settled into it.
Keep in touch. I'd be glad to help you out as much as I can.