Search Results: seeking a girlfriend

See title. Related to previous question about girlfriend acting attention-seeking (like a "single" thristy teenager) and posting on Snapchat, Instagram/My story and Facebook, generating a lot of male attention in private messages. I claim it's attention-seeking and annoying, but my girlfriend is acting oblivious and think I'm overreacting. She's an Instagrammer with a bit of following, and I don't mind her being a bit narcissistic and posting pictures (including sexy ones), but it bugs me when she's doing this attention-seeking (?) stuff - especially in private channels like Snapchat, like she's just fishing compliments and flirts. I mean, she has a boyfriend.

What's your judgement?

So my girlfriend is a bit younger than me (21 years old) and has always been interested in the way she looks, and using her looks to gain social media following. She has 10k+ followers on Instagram, and regularly gets compliments, private messages and friend requests from thirsty guys in her home town.

My issue is not that she's using social media to post pretty pictures (modelling, stylish, sexy etc) but it feels like a warning-sign that she's still, while in a long-term relationship with me, posting the kind of attention-seeking selfies (pouting lips, only selfie, posing body-pictures etc.) on Snapchat/Instagram/Facebook (and stories - which are seen by all those hungry guys) and defending her social media usage from all criticism and jealousy. I just feel like she's fishing for attention and it's bothering me that she doesn't listen to my concerns.

MY QUESTION: Is this a behaviour that's so normal for girls these days that I should just write it off as an age-related behaviour, or do I have any justification in feeling like it's not very girlfriend-like behaviour and a legit red flag?

Would love to hear if someone "is" this girl/what you think, or if someone has found a nice way to overcome the feeling of weirdness together with their partner. Advice much appreciated!