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The chances of her being pregnant with the second guy is more since she is likely to be in her fertile period at that time and the unprotected intercourse with ejaculation inside would possibly result in pregnancy.
Having depression is common in pregnancy. Support her with all means and help her realise that she has a baby growing inside her and she should take care of herself and the child. If she did not want to get pregnant, she should have taken measures to avoid it in form of birth control measures or emergency contraception.
If she does not want to continue with the pregnancy, let her discuss about safe measures for abortion with her gynecologist, rather than thinking of suicide.
Take care.