I wonder about this topic so I want to send this idea out there:

I wonder how Mordred feels about her rebellion?

I think, like the many events in her short life, there's a sense of dissatisfaction about it. I don't think she believes it was 'wrong'. In terms of lashing out against Arturia, she'd probably consider it alright. But I think she wouldn't be happy with how she went about it.

She'd probably hate in hindsight how she involved the citizens in her petty vendetta, likely seeing a reflection of how her mother acted.

She'd probably hate ambushing Gawain and not killing him in a straight fight because, deep down, she admits she didn't prove herself better than.

She'd hate that she never made a good point against Arturia and wanted to make a true point against her, like an actual successor would.

And she'd probably hate that she actually killed her father, since even in death she was still bound to the throne.

I don't doubt in these senses, she'd consider the one act she made for herself a failure, even if she'd never admit.