Am I right to suspect my cousin is cheating on her Army boyfriend?

I've become a little suspicious about my cousin Izzy and her relationship. She has a boyfriend who is in the Army, and they originally met through work before moving into a flat share together. Since he joined the Army, he's not around much and she is effectively living alone in their flat.

Recently, I've noticed she's been spending quite a bit of time with another man. He's much more conventionally attractive, has aspirations of becoming a travel influencer, and the two of them regularly like each other's social media posts. She also shares pictures of him, where they look very happy, laughing and joking together. What's particularly interesting is that she doesn't show her boyfriend's face in her posts, despite him sharing pictures of himself on his own social media. I wonder whether she's perhaps not particularly attracted to him. If im honest her boyfriend is very unattractive, he's surprisingly not very masculine for a soldier, is fat, short with pink hair. he's your typical soy boy.

I'm also conscious of the wider family history. There seems to be a pattern of infidelity on my mum's side. Both of the women in the previous generation were cheated on by their husbands, and the impact of those relationships appears to have affected their daughters. One of those daughters eventually cheated on her own boyfriend, who was quite similar in personality and appearance to Izzy's current boyfriend.

Izzy also has a reputation for being manipulative and knowing how to get what she wants. I haven't spent enough time around her and her boyfriend to judge their relationship properly, so I don't know whether anything is actually happening. However, I can't help wondering whether she's becoming interested in someone she considers a better prospect while keeping her existing relationship going.
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And it is my business because she's like a little stister to me even though she isn't always prefect she needs healing and I feel like i should be keeping a close eye on her to make sure she doesn't repeat history
Am I right to suspect my cousin is cheating on her Army boyfriend?
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