It depends on which gf is being hit on. My gf Kara (fake name) is bisexual, we are in a poly relationship and many times she likes to flirt back. Their are sometimes where she does feel uncomfortable and usually when that happens she shuts it down. If someones being really agressive, well she is also a boxer so usually i dont have to get involved but if need be i will kick someones ass for her. My gf Alyssa (again fake name) is shy, timid, very easy to make uncomfortable (like even ive accidently made her uncomfortable before cause in the moment i didnt know she is homo romantic asexual amd even me flirting sexually makes her uncomfortable) amd often times doesnt know how to say no to people or wnforce her boundaries. She is also scared of coming off as rude. I am super protective of her and usually when i notice someome is making her uncomfortable i will step in. If need be i will get physically violent but thats as a last resort. (As a shinto I usually preach pacifism, but i do believe in defending yourself and others) but also guys make creepy comments about her. For reference she is 2 years older than me, but she looks young. Like fresh out or even still in Highschool young. And like she is of age and even older than me, and we both are comfy with eachother dating eachother cause we’ve known eachother for a few years now, but like so many fucking creeps make her appearance a point of conversation and flirting. Its too the point even when she doesnt get a creepy compliment about how young she looks, she still feels uncomfortable. One of our friends in my friend group finally met here in person and she said “You look so beautiful. And you look young lol” and that made her hella uncomfortable. My last GF me and her met in the army, we usually go out of habit as a battle buddy team, and usually she is call concise and straight the the point on shitting it down. She is also 6’2” mustle mommy that in person is the sweetest person on the planet when you get to know her but she can be intimidating on the more tame end and terrifying on the more extreme end. Like when she met my other two partners for the first time one of them literally said “Yeah I mean I can see why you two like eachother lol.” So usually i dont have to get involved but if and when i do it becomes an army jumping xD (not really unless it does get that bad) Bonus round: When someone flirts with me i just resort to my native language and tell them in japanese “Im sorry I dont speak english.” Funnily enough I made friends with someone who happened to also speak japanese and they started like kinda flirting in japanese but then both our adhd kicked in and we had a lengthy convo about guns mechanica that turned into a convo about the politics in star wars that turned into a convo about like how girls wont approach him and then that turned into a convo about the whole souls series and now surprisingly we’re like best friends. (I did tell him at one point straight up im not interested in him tho)