She definitely seems underweight, and that may be what you're seeing. It may be that she's just shifting her weight to one side or the other, causing her to be "mis-aligned". As she gains weight you probably won't notice it as much. I had a scrawny adult male BP come in as a rescue that only weighed about 1200g. and looked very similar to yours; he's up to 1800g. now, and I don't see it at all. And a schedule of properly sized food once weekly will be all you need to keep her gaining healthy weight.