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If the girl was in her fertile period or ovulation time (time of egg release from ovary), then chances of pregnancy is present. The lubrication fluid or pre-cum that men get when sexually aroused is known to contain sperms in it. Chances of pre-cum being present with sperms in it are high after masturbation.
Ask her to consider taking emergency contraception after discussion with her doctor/healthcare provider if 72 hours are not yet passed after the act. Look out for any new symptoms development suggestive of early pregnancy like: breast soreness, nipple sensitivity, fatigue, nausea, constipation, increased sleep, hunger and tiredness, mood changes, headaches, back pain, lower abdominal cramps, increased frequency of urine.
Take care.