This is figurative language. Excluding the Sun, stars are always the same distance away from us - at least, in any meaningful or perceptible sense.1 Likewise, the sky doesn't actually get any lower or higher, but sometimes it feels like it is. Around here, when the clouds are dark and thick, it feels like they're so low you could bump your head on them. In Montana, the mountains ringing the wide open prairies make you realize just how huge the sky is - which is why they call it "big sky country."
The phrase "low stars" has no exact meaning, except to say that the stars seemed especially close. Perhaps that's meant to make us feel cozy, or maybe claustrophobic. Hopefully the surrounding scene makes that clear.
1: You can try a little experiment at home. On a clear night, look at a star with your naked eye, then look at it with a pair of binoculars, or even the most powerful telescope you can find (for home use, not an observatory telescope). The star will look the same size, whether you're looking at it through the telescope, or with your naked eye. Now try looking at the moon, or a planet in our solar system, if any are visible.