That's a really annoying comment by your dh isn't it? Formula does not necessarily mean a longer sleep, despite people's assumptions!!
At 6 months your dd is just starting solids but probably isn't having a huge amount to eat. I think it likely that as she increases her solid intake (which might happen really quickly) her night wakenings will decrease and then stop.
My ds is 13 months, still breastfed, never had a bottle. He generally woke once in the night (about 3am) till 10 months, then also dropped his 11pm feed just very recently.
I do remember times of him waking 2 or 3 times in the night though (brutal!) and it was probably around 6 months.
It will pass, and my guess is it is just due to your little one probably needing to up her solids a but,which she will do naturally over the next few weeks.
Chin up,and ignore dh comments, no need or reason to switch to formula at all, especially if you are happy to bf.