There is a lot to unpack here, but I haven't really seen much in the way of social awkwardness or social anxiety from Aurelia, although I admit I may just not be remembering. ALl instances of Aurelia I remember have been with either Clinton or Claire, and never have I seen an indication of social issues with her.
I am wondering why you call her behavior "abnormal". Perhaps you simply mean different from what the average middle-aged single mom tends to be interested in? Her behavior seems perfectly normal to me, if perhaps outside of what we would expect from somebody in her position. That's really more on us and our preconceived ideas of what people might/should engage in, though.
Edit: I do agree there are quite a few signs of Aurelia avoiding issues. As far as 'deceiving', she didn't deceive or conceal it from her kids, and there is literally 0 reason for her to go around telling people what she does in her spare time, just like I don't go around telling people what online forums I visit.
My view is that her first dropping herself in it in regards to her comments about Claire getting a job followed by her reaction both to Claire after they left indicates to me that she is 1) unintentionally being socially awkward and 2) catastrophising to the point where she's attempting to self medicate with cannabis to ease her anxiety. In this example, she quite clearly instantly goes straight into catastrophising about what Claire might think about what she had just said - to be fair Claire has also done the exact same thing though more about what people might think about her continued inability to get a job in her chosen job field. Thats social anxiety. If you instantly freak out internally and disassociate because you think that you might have offended someone - regardless of what that person might actually think - then thats social anxiety and awkwardness.
Her behaviour regarding her vtubing channel is abnormal not because her chosen hobby itself is outside of the norm but because of how she's ended up doing it. Loneliness feeds a desire to get attention from those nearest which leads to abnormal behaviour in order to get said attention. To put it another way, if Aurelia decided to start a baking youtube channel I doubt that would have garnered as strong a reaction from either Claire or Clinton compared with essentially delving into furrydom and therefore subconsciously Aurelia would not get the attention it feels it needs.
Being deceptive isn't just flat out lying to someone, it can be someone doing something which people might find displeasing under their noses and when challenged arguing that because they haven't explicitly lied about it so therefore no harm no foul. TL;DR you don't have to lie to be deceptive. As an example, a child might decide to take a toy to school even thought the school has a no toy policy. The child doesn't declare that he/she has a toy to the parent or the school and for a month or so he/she happily comes and goes with the toy in their bag. When the toy is eventually discovered and the child challenged, he/she explains that because they have been taking that toy into school for so long they thought it was OK knowing full well that isn't the case. Thats deceptive behaviour.
To put this into Aurelia's case, consciously she might not be all that clear on the ins and outs of what she is doing or aware that her appearing as a 3D cow with multiple breasts might be on the fringe of what society might find tasteful. However, subconsciously, she's overtly doing this 1) as a way to alleviate boredom and 2) to garner a response and therefore attention from those nearest to her when her hobby is eventually discovered.
As a note, none of this means that any of the Augustus family have serious mental health issues, these are things which challenge us all be we neurodiverse or neurotypical. Its just up to us to recognisise our negative behaviour and try and work on ironing things out is all