Is it normal for other guys to hit on my girlfriend (19, F)?

She and I have been dating for three years and she is super attractive and wears shorts, mini skirts and dresses. She gets hit on quite a bit and I only step in when I have too.

she says it makes her feel so uncomfortable when others hit on her or try to get her number.

Is it normal for other guys to hit on my girlfriend (19, F)?
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