Emmi which LC did you see? Have you spoken to Penny or Sandy? They were both so helpful and Sandy does home visits too
Also, I'm so suprised LLL couldn't help you....I nearly rang you yesterday actually to see if you wanted to come to a meeting with me too lol
I've found them awesome and not at all the BF nazis I was told they'd be lol 
You're doing a good job and well done for sticking at it. You *will* find a solution..it's just finding it that's frustrating! 
Babies are all so different....BF doesn't need to drop off once solids are introduced, but they might too IYKWIM? Also, with all due respect, I think you're buying into the story we're told that having mastitis affects our supply and also that Lilla 'has' to feed a certain style/way/length of time etc to be satisfied. IMO giving her a bottle as a top up may well be hindering. I'm absolutely not an expert at all tho...just using my experience to date of having lots of issues as well, not entirely dissimiliar from yours in some ways! 
Do you think Lilla just may be keen to BF little and very often at this stage? It doesn't mean she's not getting enough if she doesn't linger for ages. Is she gaining weight ok?
Aaawww I just wanna give you both a big hug and say hang in there. I absolutely have faith you guys will sort it out and come to a solution that suits you both down to the ground. 
Nic- lol at you trying the sitting upright position with Lily! SO cute!
Clodagh LOVES it and even does the 'milk' sign to her Nana and my friends if she's sitting on them that way....God loves a trier!! 