There is a lot of misinformation out there about autism. There is no "one size fits all" with a diagnosis of a medical condition that is known as a spectrum disorder and has all manner of different presentations. Sadly vast numbers of the population are ignorant about most things - and chose to remain so - so it's not surprising that you are encountering ignorance about autism in your family.
I would suggest you ask your daughter's doctors/therapists for suggestions of an excellent introduction to autism book (I hate to say it, but you want whatever is the "autism for dummies" text...just with a kinder title). Hopefully it's a book or online-based guide that is relatively inexpensive or free. You could, if finances permit, buy a few copies of that book (once you've read it yourself of course) and give them to your close family members (mum, sisters etc) so they have a common source of information/guide that they can refer to that you agree explains autism well. Share this information at a time when moods are not fractious and unpleasant. Accompany the book (or if you aren't able to buy books then share a link to the book, or an online version of whatever information you want them to read) with a note that is kind, open, and says something along the lines of the fact that the diagnosis was a surprise to you and understandably a surprise to them, that you've had to learn a ton about autism and are still learning, and that you've come to understand that there are lots of different ways it can present.
You might feel comfortable listing (kindly!!) a few ways in general that autism may present (don't make it specific to your daughter - that could be rather unkind if she is in a position in future whereby she can read that letter and her situation is changed). So: in terms of the "touching" issue: children may not understand social boundaries and cues when it comes to physical contact. They may reject contact that is seen as normal (shaking hands, friendly family greetings like hugs), or may misunderstand social norms and initiate greeting-type contacts too often because they cannot read body language cues telling them that the other person is uncomfortable (for example, hugging during play, or using physical gestures because they have difficulty verbally communicating how they feel). Etc etc.
Many people assume that autistic people LOATHE physical contact because that's what they have seen in movies - but of course that's not real life. For example, many people assume that "Rain Man" is an accurate movie about how autistic people behave: but the Dustin Hoffman character in that movie is based on a real life gentleman called "Kim Peek" - who was thought at the time to be an autistic savant, but is these days thought to actually have had "FG Syndrome". The point being: people who have autism are NOT all like Kim Peek, in fact it's difficult to find many people at all who are like Kim Peek (he had a number of developmental differences in the way his brain developed, for example he lacked the typical connections between the right and left side of his brain. He had the amazing ability to read both pages of an open book at once; the left eye would scan the left page, while the right eye would read the right...this is, of course, not at all typical of a person with autism!).
You may also find that various of the Autism support charities already have these kinds of guides and "how to talk to your family/friends" documents that are pre-written for you - so take some time and search them out, and make them available to people you think will have contact with your child. It will give you a common frame of reference. You can, of course, just ask people what they think autism means and what they think of when they think of an autistic person. The point with that is not to play "gotcha" or to make those people think they are stupid or uninformed, but to assist you in understanding where there may be differences in understanding.
You may also want to ask your child's teachers/educators (you say she's 5 so presumably she either has had kindergarten teachers already, or you are preparing for her to attend primary school) if they have they have SENS information and guidance that may be useful. They often have to explain what autism is to other students when an autistic child is in the same class. And they will have strategies for how to manage children who have differing understandings of social norms/behaviours/cues etc etc - including the "touching" issue that seems to be causing the most angst at the moment for you and your family.
Hopefully this all gets better with time and with people in your family and friend circle taking the time to educate themselves. If they care about you and your child they should want to do that, but people have their own busy lives and difficulties so it's important to make that process as drama free and accessible/easy as possible. And be open if they have questions and forgiving if they get things wrong or are awkward about how they ask. It is very difficult to know what to say and how to behave when someone shares information like that - because they don't know how you feel about the situation either (and you're still figuring that out yourself), so there is a certain amount of eggshell treading and uncertainty all round.
If you haven't already I would certainly urge you to seek out therapy yourself to help you cope with your child's diagnosis and behaviours. Frankly I think everyone benefits from therapy and learning more about themselves and how the interact with the world, so please do not view this as a negative thing. I would also urge you to seek out talking therapy for your autistic child and any other children you may have - it's helpful all round.