Well, it really depends on which tense you need to use here. Here are the options:
Ella viene a la fiesta - present tense
Ella vino a la fiesta - perfect preterite, used for recent past time like yesterday.
Ella venía a la fiesta - imperfect preterite, used for remote past time like years ago.
Ella vendrá a la fiesta - future tense
Ella vendría a la fiesta - conditional tense
Ella venga a la fiesta - present subjunctive
Ella viniera a la fiesta - preterite subjunctive
Ella viniere a la fiesta - future subjunctive.
