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occurs when there is fertilization between sperm from male partner and egg from female partner. If there is no penetrative intercourse, it is very unlikely that any semen has come inside vagina for fertilization.
Theoretically, it can spread if the finger was contaminated with semen. There is no way to know/rule out whether that happened in your friend's case with cent percent surety.
If your friend is really worried, she can take morning-after pill so as to relax from worry from risk of getting pregnant.
Dr Tejas Shah