If you want to give a bottle at lunch time, then that is of course, absolutely fine.
I personally found that in the early days weighing helped build my confidence, but that was obviously because DD went up the centiles then followed the line exactly. Had her weight gain have happened differently, then I might have felt very differently about it. Now (and she is much older, 8 1/2 months) I don't get her weighed and haven't done for ages, but I know she is fine by her nappy output, but most of all, just looking at her. It's obviously much easier to be relaxed with an older baby, especially once they are on solids.
I think one thing to keep in mind is that the red books suggest weighing monthly for a reason. If your DD was weighed once this month and hadn't gained much weight, you might find that the next month she had gained loads. One weigh in of not much gain wouldn't worry you I expect, whereas weekly weighing means that in that month you'll have more weigh ins of not much gain and so it will worry you more, naturally. (I hope that makes sense)
Also, HV's just don't have much experience of BF babies, because not many babies are BF for very long, so it's natural they'd feel less comfortable with BF babies, because they really are very different.
Have you considered other options to help with daytime naps, such as a sling? Even if your DD doesn't nap in it, you'll be able to get more done and be more mobile. If it helps at all, my DD didn't nap in the day unless being held for months. Then suddenly she would nap in her cot for 20 mins and now she'll sleep in there for up to 3 1/2 hours. It does get better, I never did anything differently.