I really wouldn't worry too much about introducing a second meal at this age, especially if it means she reduces her milk intake. Milk, whether breastmilk or formula, is supposed to be your baby's main source of nutrition at this age and solids are just an extra to get them used to different tastes and textures. I'd suggest talking with your child health nurse for advice, but from what I know it's more important for babies to have their milk than solid foods, it's not recommended that you start giving solids before milk until around 8 or 9 months. If she is still gaining weight, having plenty of wet nappies and fairly content it's a pretty good indication that she is getting enough to drink/eat. Try not to stress too much about it, she'll let you know when she's ready for more food. My daughter is nearly 8 months old and has only been having 3 solid meals for about 2 weeks, I didn't start her on solids until she was 6 months and for about the first month she was only having 1 meal per day. As you said, your daughter is healthy and nice and chubby so it sounds like you are both doing well. I hope this helps.