Her blood pressure runs a bit low — she needs more rest.
Tips
grammar
偏 + adjective forms a common pattern meaning 'somewhat too…' or 'leaning toward…': 偏高 (a bit too high), 偏大 (a bit too big), 偏少 (a bit too few), 偏贵 (a bit overpriced). The implication is 'compared to what's normal or expected.'