She’s right and I have noticed this about Saki. In fact, when I stopped to think about it, this all goes a lot deeper than her sexuality.
I struggle to think of any instance where Saki was with another person and they did something she wanted to do, though there are plenty of times someone else pushes her into doing something for them without her really pushing back at all. I also can’t think of a time where someone did something that made her uncomfortable and she stood up for herself, as opposed to shutting down or running away. I’m not even sure what Saki likes beyond girls and piano, and even the latter was a more recent development and something she struggled to express even to Kanon.
Apparently, she’s been like this since she was a child. It sounds like it started when her mother had to take care of her grandmother and Saki was no longer the priority she should have been, so she stopped prioritising herself. I find it telling that part of what made her piano recitals important to her was because she got to be centre of attention, especially for her mom. It also makes sense in retrospect that her first crush was someone who during their limited time together gave Saki her undivided attention. No wonder Saki stuck with piano for so long despite only recently starting to like playing it.
Even with Kanon, while Saki was the one who pushed for the relationship to happen, most of what they do are things Kanon wants to do. When Saki does or says something that rubs Kanon the wrong way, she speaks up and it gets resolved fairly quickly. When it’s the other way around, Saki can’t do the same and it leaves behind this weird tension that lasts for weeks. Saki is not the only problem though, to her credit, she has taken a lot of initiative to learn more about Kanon and suggest doing things the latter wants to do, but we haven’t seen Kanon do much of the same for her.
What I’m saying is, there is a clear imbalance in how their relationship has worked up until now that somehow just barely worked when they were just friends, but it’s not enough anymore. Now they have to work to find their equilibrium which is a process and not something that can be forced.