Is it unjustified for me to experience feelings of jealousy?

Is it wrong for me to feel jealous in this situation?

I've noticed that my girlfriend has made a new friend at university this semester. They have been spending time together, and even in a picture that her friends took of them, they drew a heart and joked about being in a relationship.

However, we've been experiencing some troubles in our relationship lately. We don't communicate as much as we used to, and when I try to initiate conversations, she often responds sporadically or doesn't address all of the points I raise. We have talked about this issue, and she claims that she's trying her best but has a lot going on in her life at the moment. I understand that she's busy, and I was there for her when she was sick for a couple of days.

Recently, she showed me a screenshot of a conversation and asked if the person she was texting was flirting with her. From my perspective, it seemed that way, but she denied it. She initially scratched out the name and refused to tell me who it was until later, when she revealed that it was her new friend.

Yesterday, she came to my house to work while I finished up my tasks. However, throughout the entire time, she was constantly texting her friend, only occasionally focusing on her work. Once we finished, she wanted to spend time together in bed and showed me a lot of affection.

I attempted to discuss my concerns about her constant texting. She noticed that I was upset by it and asked why she doesn't text me in that manner anymore. We had a discussion, and she reassured me of her love and stated that if she ever developed feelings for someone else, she would inform me and that I needed to trust her. We ended the conversation on good terms.

However, throughout the night, she continued to be engrossed in her phone. As she was leaving for home at around 12 am, she kept texting her friend non-stop. I tried to take a glimpse at the conversation, which upset her. She mentioned that she values her privacy and we deescalated the situation. She continued texting him incessantly and asked if we were okay, urging me to trust her.

When she arrived home at 2 am, I attempted to text her, but she remained online without responding until 2 am. During that time, she replied to my messages every ten minutes, claiming that she was talking to a female friend or that she left her phone on while changing into her pajamas. I expressed that I would stop messaging her as frequently since she felt overwhelmed, and I reiterated that she loves me. However, she expressed that she genuinely enjoys talking to her friend as he makes her laugh and that I make her feel like she's doing something wrong. This made me feel terrible, and we began arguing again.

She told me that she was planning to sleep at 1 am but remained online. I explained that our relationship was built on conversations and that it's crucial to me to have at least five minutes of uninterrupted, fluid conversation with the person I love, which she always seemed to have excuses for. However, I observed that she was conversing with her friend just like we used to.

At this point, she mentioned that she needed to think about everything and requested space. She no longer wanted to continue the discussion because she's tired of the topic.

In other words, I'm unsure if my feelings of jealousy are justified in this situation, and our conversation took a tumultuous turn as she expressed her exhaustion with the subject matter.