Sleep development is not linear and often goes backwards or changes. There are talk of 'phases' and 'regressions' but I actually think both of those words are not useful in terms of sleep development.
It being a 'phase' or a 'regression' suggest that if you just carry on and don't change anything, that sleep will go back to how it was in time. I disagree fundamentally with that view, which is why I prefer to explain in terms of development being non linear.
Parents have to change things, try new things. What once worked at one point may not work in later months and so parents have to keep on changing their approach. If sleep gets worse, it means that what you are now doing (and have been doing quite successfully for some time) no longer works and so a new approach is needed now that baby's needs have changed.
So language analysis aside, I would suspect that your DDs calorific need has increased. At 16 weeks old there will be a lot of physical and emotional developments happening and all of these new skills and abilities mean she needs more calories per day. She may well be waking in the night for feeds because she needs those feeds - she needs the extra milk.
I know what you mean about shock to the system. My DD was sleeping 11pm-8am without a feed while EFB from 7 weeks to 12 weeks. She then started needing more milk. My answer was to start mix-feeding, but that's because DD is my fourth child and I am not so precious about breastfeeding as I was with my first. I am not suggestion you need to give formula milk. But you could do if you wanted to.
Alternatively, try feeding far more frequently through the daytime. Or just embrace the night feeds as special cuddle time and accept that they are part of the baby months.