For the 1st year of life... a baby's PRIMARY source of nutrition is from breastmilk or Formula... NOT solids and NOT other liquids.
This is per our Pediatrician as well. And they NEED to be fed (breastmilk or Formula) on-demand.
IF you are giving her solids... BEFORE nursing/Formula.. then this will cause a baby to WEAN from breast/bottle. You do not want that to happen. Always nurse/give the bottle, BEFORE solids... otherwise the baby will be too full, to nurse.
Next, my kids were all tall/big babies... 95-97th percentile for height and 50% for weight. My kids, as babies, were NOT "skinny"... but lean. THAT is what our Doctor said, and was very positive about it. They are also very healthy and nursed well.
I did not start solids with them, until 6 months old. And even once they began solids, I ALWAYS nursed them PRIMARILY, on-demand, and 24/7. At that age, 5 months, my kids were still nursing every 3 hours. Or less... if on a growth-spurt. They were healthy, and grew like weeds.
My advice would be is, I do not agree with your Ped.
Solids should not be her "main" intake source. At this age, "solids" are only an 'introduction' to foods.... pretty much for the 1st year. It is NOT their main food. Breastmilk or Formula should be.
Yes, solids is interfering with her bottle intake. To me.
Feed her her bottle or nursing, ON-demand.
How often are you giving her solids?
At this age, it is not 3 times per day. Just 1 time. 3 times a day "meals" are something gradually built up to... over the course of the year.
Do you feed her her bottle according to a schedule, or on-demand? Perhaps, feed her on-demand.... because this is more reflective of a baby's needs for intake, than on a 'schedule.' And when she has a growth-spurt, it is even more important to feed a baby on-demand... otherwise their intake will not keep pace with their growth.
ALWAYS nurse/give bottle, BEFORE solids.
all the best,
Susan