Can someone help me with a translation?

Hi guys,
I'm writing because I'd need some help translating a couple of sentences. I'd be really grateful if you could give them a look.

"どうして平気でいられるの？私のことなんか、放っておいても平気だっていうことじゃないの？"
This is a girl talking to a boy. I think she's asking him why he's ignoring her, but I'm not sure.

"電話くれるって、言ったじゃない。嘘つきなんだから。"
The same girl's speaking. I think this means "You told me you would call me. You're a liar", but I'm confused by the usage of んだから and くれる: shouldn't it be あげる?

何よりも会うことが大切なのに、会って、お互いの温もりを確かめあうことが必要なのに、「元気？」「まあね 」というやりとりだけでは、何も伝わるはずがないではないかと言いたかった。
Something like "She wanted to tell him that there was nothing more important than meet up and make sure of each other emotions, but with a simple exchange of "Hey, how are you?" "As usual" (on the phone), nothing could be transmitted.", but I really can't understand why のに is used.

(sorry for the awkward English :sorry

Thanks a lot for your help!

Julieta said:

"どうして平気でいられるの？私のことなんか、放っておいても平気だっていうことじゃないの？"
This is a girl talking to a boy. I think she's asking him why he's ignoring her, but I'm not sure.

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She is asking why he is staying calm, and presumes that his calmness shows he is unconcerned with her.

Julieta said:

"電話くれるって、言ったじゃない。嘘つきなんだから。"
The same girl's speaking. I think this means "You told me you would call me. You're a liar", but I'm confused by the usage of んだから and くれる: shouldn't it be あげる?

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～（な）んだから performs as a kind of sentence final particle. It's used for conclusion here.

電話してあげる is a direct quotation 'You said "I'll call you"', whereas 電話くれる is an indirect quotation 'You said you call me'.

Julieta said:

何よりも会うことが大切なのに、会って、お互いの温も りを確かめあうことが必要なのに、「元気？」「まあね 」というやりとりだけでは、何も伝わるはずがないでは ないかと言いたかった。
Something like "She wanted to tell him that there was nothing more important than meet up and make sure of each other emotions, but with a simple exchange of "Hey, how are you?" "As usual" (on the phone), nothing could be transmitted.", but I really can't understand why のに is used.

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温もりを確かめあう more likely refers to physical contact.

お互いの温もりを確かめあうことが必要なのに、それをしないで「元気？」「まあね 」というやりとりだけでは･･･

Thanks a lot for your answer, now I got it!