If you get a pre shott under 200, I would wait and retest in 20 minutes, without feeding. You want to make sure the number is rising, not falling and that it is 200+. 155 is a nice nadir but not terribly low. I'd guess you'll get a shoot able pmps, unless she is not yet at her nadir. If she continues to drop but you wait and have a shoot able nadir, I'd lower the dose a little.
Glad the lower carb seems to be helping!