<human>: Can you succinctly summarize the text in 1-3 sentences?

FULL DISCLOSURE: I'm writing from a foreign country, for someone else. I used "my" in the title for convenience, but I'm really a translator for a friend who wants broader opinions from other cultures, especially Western ones. For all intents and purposes, though, please assume that this is me. 
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I've dated "Carmen" for 2 years, and it's been wonderful. She spent some teenage years abroad in the United States, and she manifests herself in more "liberated" ways than other women here. Sex life has been good, too. We recently went on a small vacation together where everything was fine. 

Recently, we had an argument about some trivial subjects, including her contributions to our dating expenses. We are both students, but my part time job pays more than hers. Still, she paid almost nothing even though she makes 60% of what I do. This would not be a problem (I can understand that she might have more student loans, more difficult family situation, etc), except for the fact that she spends irresponsibly on her personal items, such as buying expensive make-up, shoes, clothes, etc. 

This "fight" led to us not talking for a while. In that time, I learned that she had gone to a male friend of hers, whom I do not know, who is a professional photographer. She posed nude for him for a series of photos, and sent them to me a few days later. While I begrudgingly admit the artistic merit of some of them, they were overtly sexual and provocative, and definitely involved full nudity. Even featured some sex toys I recognized (no penetration of any kind, however). She also hinted that she thinks the photographer is interested in her, but maintained that she did not "do anything." 

I'm at a loss. I can't even figure out what is going on in this girl's head. I don't know if I should be mad or how much. The original argument seems to pale in response to this. How do I respond?
<bot>: Girlfriend posed for nude photos without telling me for a photographer friend who she claims showed unreciprocated interest in her, and then sent me the photos. Completely lost on how to react.