I think her numbers make sense. She may be a transient diabetic or her pancreas may be healing. Regardless, she seems to need a tiny bit of insulin to maintain her numbers in that healing range. I'd continue to do just what you are doing. When she is in the 170 -200 range at preshot, give her .25 or .50 units (depending on how low those doses take her midcycle. You don't want her dropping below 40) She may start maintaining herself in the range without insulin at some point, when her pancreas kicks in.
Some people here free feed; some feed at prescribed times (most often after the shot and midcycle) It doesn't seem to bother the cat either way. There is a a school of thought that suggests if her pancreas is healing, small frequent meals will support that.