Personally I would cut out the two night feeds before dropping any more daytime feeds. I assume you plan to cut those soon anyway if you are weaning. I would keep the three feeds a day until 12mo and then replace the midday feed with a snack. Formula is more nutritious than a snack but by 12mo she should be able to get sufficient nutrition from solid foods as long as she is eating a balanced diet. Does she eat solids well?
Two months is a long time at this age in terms of development so waiting that extra two months will mean she is more ready to cut out the breast milk. I personally wouldn't introduce formula only to cut it in a couple of months but if you relly want to stop that BF now then I would offer formula in a cup, not a bottle as it is recommended to stop using bottles by 12mo.
If you do choose to keep the night feeds for now then you would be fine to cut the midday BF and offer a snack as she would still be having 4 BFs in 24hrs which would give her sufficient breast milk. As I said though, I'd be looking to shift those calories to daytime feeds first.
I suspect your HV doesn't want you to introduce a bottle of formula and then not manage to wean it by 1yo. Bottles and formula are bad for teeth and if babies are still drinking formula after 1yo they *may* not eat sufficient solid food as formula is very filling. And obviously solids is the direction you want to be moving in very soon.
Of course, I don't know your reasons for wanting to wean at 1 yo but I just wanted to make sure you knew that the WHO recommend BFing until "2 years old and beyond as long as mum and baby want to", so there is no reason you have to wean at 1yo. It is fine (and recommended) to carry on with one or more BFs alongside solids for as long as you want after 1yo. It's not the same as the recommendations for stopping bottles by 12mo. You may have your own reasons of course and that too is perfectly fine as well