Jenny, some good stuff already here for you
It's a real shame your HV has made you question yourself. Perhaps you can talk more at length about this with her and ask her for more information about why she thinks what you are doing needs changing. You have a clearly healthy, thriving little boy whose nutrition is appropriate for his age and needs as far as I can tell. I think the HV may be confusing her knowledge of formula feeding with breastfeeding - breastfeeding is food and drink to your baby,as well as an important part of her relationship with you, and as breastmilk contains iron, in an easily available form, it's of no concern that a baby of your dd's age continues feeding a lot, alongside getting solids...and it is normal for the intake of solids to be small at first, and increase over the next few months. Your HV is, I think, concerned that the bf is taking the place of the solids she would otherwise have, but this is a pointless worry at 6 mths - solids are alongside breastmilk for about the first year, and extra to it, not instead of it.
The risk with shovelling solids into a baby who is not all that interested is that meal times become a battle ground!
If your baby was a year, and still having only half a jar of solid foods then it would be justified to explore how to tempt her a little more with different things.
Baby Led Weaning is a good option to explore - with BLW, you really don't need to measure how much your baby has (you say you are measuring the fruit puree) and as the baby is the one doing the feeding, you can be confident she will take what she needs. Perhaps you can talk about this option with your HV.