Welcome to YT
I'm not too sure how to work the weight out of your puppy (I
think you double the weight at 12 weeks - but I'm not 100% sure) I think the weight of the parents can give a good indication - but it's not always the case....Twinkle's mum was 6lb and her dad about 3lb, but she's just over 8lb now at 11months old....so it doesn't always work out that way. (I'm sure someone more knowledgeable than me will be able to give you a better answer than that!)
This is a great site for learning so I hope you enjoy it here
Can't wait to see some pics of Lillie once you have her home xxx xxx