Catalyzes the insertion of one atom of molecular oxygen into position 2 of the phenyl ring of 3-(3-hydroxyphenyl)propionate (3-HPP) and hydroxycinnamic acid (3HCI). 3-(3-hydroxyphenyl)propanoate + H(+) + NADH + O2 = 3-(2,3-dihydroxyphenyl)propanoate + H2O + NAD(+) (2E)-3-(3-hydroxyphenyl)prop-2-enoate + H(+) + NADH + O2 = (2E)-3-(2,3-dihydroxyphenyl)prop-2-enoate + H2O + NAD(+) Aromatic compound metabolism; 3-phenylpropanoate degradation. Belongs to the PheA/TfdB FAD monooxygenase family.