There seem to be a couple things going on here... one , your baby is 8 months old so it would be time that your milk would be naturally decreasing some because she is getting more from solids... and the less and less she nurses, the less you will ever be able to pump. Remember that a pump isn't NEARLY as efficient as a baby being able to draw milk out.

She also could be going through a growth spurt developmentally.And many babies when they start to learn how to crawl, walk, play more etc... with motor skills, then they tend to give up on eating for a while. If she is developmentally where she needs to be you can stop worrying. If her body is telling her she doesn't need it, then unless she has a genetic disorder you haven't shared with me, then her body is correct.  Don't worry about percentiles. they matter nothing in the grand scheme of things. Some kids are larger, some are smaller. and none of them are abnormal. when looking at percentiles, you want to watch to see if the growth tends to stay the same in height and weight...  if shes about always in weight at 25ish... and height in 50 ish etc... then its not big deal... if she has been 25 in height and weight and suddenly weight drops to 5 percent and height is the same or larger , then nutrition can be an issue. But you would KNOW something was wrong... like she would be a year old and not crawling... developmentally there would be a sign if she is not thriving how she should. so take deep breaths.. all is well here... it seems to me.

If she is preferring the solids, then get some barely cereal and ad breastmilk to it. She may just be going through a strike and will take it back up again, or again it might be developmental. If you add your milk to her foods, then she may take it that way and at least shes getting it. Or , maybe she doesn't want the bottle. give her a big girl sippy cup  and see what happens. she may just want to be more socially like you :)

with pumping since she was 4 months old, you missed the growth spurts she would  have been able to go through while nursing... and she has another coming up too. So through her growth spurts you would have needed to pump twice as much to continue building the supply.  the best way to build supply is demand. if you start pumping every 2 hours for 15 minutes for a week, your milk supply will increase. The body knows that after certain amount of time, if there is no growth spurt then it must be time to wean... we have very intelligent breasts  :)  plus, your anxiety may be causing low milk as well...  

My biggest suggestion would be... relax as much as you can... easier said than done. Trust your daughter that she knows how much food and what she needs to eat... Her body gives her clues that only she can know... Don't force food , just let it be.. She will thrive  an you cannot force her to eat anyway ...She may be one of those babies that wean early... try all you can to add breastmilk to anything she takes and rest assured you have done better than most moms do with nursing... ANY breastmilk is better than none.

So relax, do the herbs if you want, and sit back and increase pumping to build it back up if you so desire. Confirm she is developmentally where she needs to be , and know shes going to be ok... if you do that, chances are, shell stop feeling the stress about it that you give off, she very well could take the bottle more often without issue, your milk supply will increase and you can relax more :)

I hope that helped and wish you the best !