Ladies, can you please help me understand what's going on here?

I have been with my girlfriend for 3 years now and all of a sudden, she has gotten incredibly possessive and paranoid about other girls trying to take me away from her. I feel like it all started a few months back when I told her I felt like I looked too young when I straight shaved. At the time, she thought nothing of it. So I stopped shaving every morning and started letting my facial hair grow out. I work in corporate eCommerce so we aren't allowed to have full on beards but well maintained stubble or facial hair is fine. I don't know if my girlfriend just finds me more attractive now and worries that other girls will feel similarly or if it's something else entirely? I asked her about it the other night and the only thing she kept saying is "I trust you, I just don't trust other girls". WHAT GIRLS though? It's not like I am texting or spending time with anyone else and I have never and would never cheat on her so I just don't understand the insecurity? I always compliment her and tell her she looks beautiful so it shouldn't be a lack of compliments causing the problem. I have always been confident and never had issues meeting women when I was single but never considered myself anything spectacular, looks wise. I'll post a picture of myself but do I really look that good with facial hair or do you think it's something else entirely?