Ren,

Firstly there probably nothing wrong with her physically as to why she doesn't like the left side as much- you can usually tell if there is an issue, for example she would not be able to turn her head to one side, or might be developing a flat spot on one side of the head. So don't worry about it too much - ask your MHCN if she can detect any reason to refer you to a paediatric physio consult or chiro before you book in, because if she can you will be able to use the public system which is free, and if she doesn't see a need then there wouldn't be anything wrong.

Secondly, your LC is right in saying the flat nipple shouldn't bother her - I have fairly flattish nipples and baby can attach as they suck it back in their throats whether flat or pointy, but she might simply prefer your other nipple as is easier and she's used to it - babies are creatures of habit like the rest of us.

Thirdly, I don't know if it would be a good idea to just express off the left one instead of feeding because wouldn't offering her a top up if she's being fussy on that side maybe reinforce the aversion and then stop her being as hungry, so then no motivation to be interested in the left boob? (Could be totally wrong, just typing as I think, check with your LC or someone more experienced of course)

Lastly, you have done such a fantastic job thus far, I'm sure you'll be back to solely breastfeeding soon. My DD's left side aversion dulled down a lot after a week or two and now even though she still prefers the right, she will feed off the left too beautifully now, and I'm sure it will be the same for you, she's just got to get used to it. I also find if Elly starts to pull off and whinge and fuss a bit, (which she does most feeds as I don't have much milk but need to encourage her to keep sucking) I get up with her and walk her around while breastfeeding and keeps her interested enough to keep sucking without complaining (though my arm's feel like lead from holding her up). So I don't know if you could try that, (think of it as Bicep Curls )