Sheena, a Half Dragon Tale
Sheena is an optional NPC added by a modification to Baldur's Gate II (SoA and ToB).
Recruitment
Sheena can be recruited by opening the left cell above Firkraag's lair. The only way to open this cell is by killing Firkraag and collecting the key left on his body, which makes it difficult for low-level parties to recruit Sheena.
Although a half-dragon, she is implemented as a Fighter/Mage, and therefore can wear any armour (but cannot cast spells unless it is Elven Chain Mail). The only exception is that if you forge armour from the scales of Firkraag, she will remove it immediately after being equipped and will return it to the PC's inventory.
Romance
Sheena can enter into a romance if the PC is male (any race) and of good or neutral alignment.