Another theme is the power of friendship. Often, the lesbian relationship starts from a deep friendship. Like in a story where two girls were best friends for years, and slowly realized their feelings were more than just friendship. They supported each other through tough times, and that friendship - turned - love is a strong theme.
Overcoming obstacles is also a common theme. It could be family opposition, like in a story where a girl's family didn't understand her relationship with another girl. But through their love and determination, they worked through it. Or it could be social prejudice, yet the two in love find ways to be together despite all the difficulties.