Lyanna struggles with her sexuality and her Northern upbringing.
Lyanna Stark was not attracted to other women.
At all.
The fact that she had blushed like a maiden after dressing in the same room as Ellaria had nothing to do with attraction. It was simply too warm that day. It was always too warm.
Lyanna did not want to bed her best friend. Northern women don't feel such things, and Stark women certainly don't.
Her gaze only lingered on other ladies because she was admiring their clothing.
No. Lyanna liked men, and her husband was proof of that. There were few men that could be considered more masculine than the Red Viper. And Lyanna was definitely attracted to him.
Lyanna knew that Oberyn liked both women and men, but it was alright for him to like both. He was Dornish. She, however, had been raised a Stark of Winterfell, and Northern ladies were not attracted to other ladies. They never thought of bedding their friends. It simply wasn't done.
Lyanna did not want to take Ellaria Sand to bed, and she didn't understand why Oberyn thought she did. She didn't understand why he always smirked at her whenever she blushed in the other woman's presence. It really was too warm in Dorne.
She had denied her attraction to Ellaria when he had brought up her recent behaviour around the Dornish woman, but he had asked her to think her feelings through. There was really nothing to think about, but she loved her husband, and she had promised to do so.
Did she like other women?
Of course not. Northern ladies were not attracted to women.
But she was not in the North anymore. She was in Dorne, and the Dornish didn't care who shared a bed, so long as the participants were willing.
Oberyn often complimented her on how well she had adapted to life in Dorne.
That didn't matter; Stark ladies did not bed other women.
Then why did she always blush and look away when another woman undressed near her? Why did she feel a shock of heat whenever Ellaria touched her in even the most innocent of ways?
Maybe she was not as much of a Stark as she had once been.
No, Lyanna Stark was certainly not attracted to other women, but maybe Lyanna Martell was.