Antonella is right, assuming the sentence is about a female is the best bet, and could be either because a generic "it" will usually take a masculine pronoun, or because of the way the speaker specifies having recently seen her. However, there are other possibilities such as "Hai visto la mia borsa/la gatta/la nuova costruzione?" so it is also accepted now :)
No. That translation does not make sense in English. Neither the "I have seen" bit nor the "right" bit. I have seen someone do something at a time in the past that is not specific. I have seen her eat snails (but I can't say when exactly). I saw here eat snails yesterday, last week, last month, on Christmas day....
Right is just a mis translation.
Based on my knowledge of French the object of the verb in this sentence must be feminine because the feminine form of the past participle, vista, was used. If the object had been male then visto would have been used. Even with verbs taking the auxiliary verb avere the past participle agrees with the object of the verb when the object precedes the verb as in "L'ho vista .... " If the object follows the verb then there is no agreement as in "Ho visto la ragazza ..." Hope that helps.