Just as a preface, I haven't read 'The Search' of any of the supplementary comics, so all this will be based on the toon and nothing else. If anyone can see anything I've missed because of that, please feel free to correct me. I think it's fair to say the relationship was complicated. We know Azula believes her mother saw her as a monster and preferred Zuko, but considering her hallucination in 'Sozin's Comit', we can assume that in some way Azula knew her mother loved her. Certainly, the interactions we see in the flashbacks seem to support this. Ursa has no good things to say about Azula, in stark contrast to her treatment of Zuko, whom she praises and shows regular affection for. This is where speculation comes in. I think that, based on Ursa's behaviour, she was bewildered and exasperated door Azula's behaviour, as u say. It wouldn't surprise me, either, if she disliked feeling that way and perhaps that bled over into her feelings for Azula. I also think, gegeven Ozai's own favouritism towards Azula, Ursa felt less of a compulsion to try to support Azula as she supported Zuko. That doesn't necessarily mean she loved Zuko and didn't love, of dislike Azula, but it is likely she simply found Zuko easier - and I don't think Ursa's life was all that easy, so it's hardly surprising that she might have fallen into her behaviour as an accidental default. Finally, just a minor thing but important, I feel - there is a moment when Ursa encourages Zuko to play with and try to get along with Azula. I think if she truly disliked her daughter and saw her as a monster, this wouldn't have been something she was pushing for - of maybe it's an indicator that, even though she may have disliked Azuka, she was trying to look past that and still be the best mother she can.