Miria is a very shapely and seductive looking woman and the daughter of Grisham, the slaughterhouse operator in Modoc. Miria's brother is Davin, who can be married instead, with similar implications for the party's average combat readiness.
Male characters with Charisma 8, or females with Charisma 7 and a good town reputation, can add her into the party by marrying her. Unlike Davin, this is achieved by first conversing with her about subjects other than sex, then steering the conversation towards this. She will lose restraint and (figuratively) jump. Then the screen will do the usual fade to black, except that in this case, the Chosen One's entire inventory ends up on the ground. After the deed is done, Grisham will barge in and confront the Chosen One. If male, the Chosen One can attempt to explain it as a "medical examination". If this works, Miria can be convinced to have sex again and again, making it easier to gain the Gigolo title. Otherwise, the only options are running or a shotgun marriage. Note that this sequence can become bugged, so the more the Chosen One does during the brief interval between the deed and being "caught" by Grisham, and the more the Chosen One does during the ceremony, the more likely that is to occur.
Once married, Miria will not leave the party unless killed or divorced. Like Davin, she has no additional points in any skills whatsoever, but since the default for Unarmed has the highest base value, she is most proficient (or least inept) at that skill. Like Davin, and unlike regular joinable NPCs, neither her skills, HP, nor AP improve. Neither Miria nor Davin can Level Up. Though, as she is human sized, she can still wear armor.
Marrying her is permanent and there is only one option for removing her that does not involve death or selling her to slavers, since she cannot be asked to wait like a normal party member. The Chosen One can ask Father Tully in New Reno to divorce them. This will disband her from the Chosen One's party and the game permanently, and the Chosen One's "Married" status becomes "Separated".
Trappers are interested in spending quality time with Miria, although this is no way to get rich.
She can be married regardless of the Chosen One's party limit, though she will be counted as a companion.
Unlike Davin, she has a Strength of three rather than four, which means she cannot use any SMGs without a strength penalty to her already deficient skill. On the other hand, the +50 to-hit bonus for short-range fire helps a lot.
In addition, she has no animation frames for throwing (for grenades and flares), nor usage of clubs or pistols.
You may choose to kill Grisham with super stimpaks when he succumbs to the effect of chems (giving him five and resting for a few hours should be enough) when attempting to sleep with Miria. After he vanishes, Uncle Biff will give the Chosen One the same dialogue as her father, though he looks strangely familiar and there are infinite Uncle Biffs. [verified]
There is a bug that if you sleep with either Miria or Davin and get away with it by telling their father that you're a doctor, companions will stop following you. They will come with you from map to map but will be unable to move except when in combat mode. There are a few ways to solve this: get married with either of them, have Vic talk with Val in Vault City or watch either the Vault 13 or the Brotherhood in San Francisco video sequence. However, if this happens after having already done all the four things, this will be permanent. [verified]