Maybe it's because I'm very sensitive about this subject due to the fact in movies and TV shows lesbian characters almost always are "de-gayed" in some way (usually simply by ending up in bed with a man and obligatory looking like they have the best time of their life), but it kinda sounded to me like she was slightly attracted to him.
When asked about him, she laughed in similar manner as she did in response to my character's advances and said that he makes her wonder about (and here she made a pause and spoke the word in a bit suspicious way) "things", thought later she brought up the Qun so it could be just it, but first she said: "he's got nothing on you" after that already kind of suspicious sounding line. If that was about Qun then why would she mention my character and how much better she is than him?
I've read somewhere here that if I didn't play as Qunari, she would say something about Bull making her wonder how Qunari women look like instead. She was expressing since the first encounter clear attraction to my Qunari. So what does that "he's got nothing on you", the speech line that was made apparently only for female Qunari characters she's crazy about, is supposed to mean? He's hot, but you're way hotter?
For more clarity, tha's the dialogue:
My Qunari: Thoughts on Iron Bull?
Sera: Hahah, he makes me wonder about... things. He's got nothing on you, but that Qun stuff, I don't know.