As a general rule, your resume should avoid using first-person pronouns. This includes your resume summary. That said, the third person sounds too impersonal – as if somebody else wrote the resume summary instead of you. Luckily, there’s a neat trick you can use to make your text flow better—just get rid of the pronouns altogether. This way, instead of writing, “She is a marketer with 5+ years of experience in XYZ,” you can write, “Marketer with 5+ years of experience in XYZ,” and get your point across just as effectively.