But I do think Celene loves Briala very much. Not even this has diminished that. And I got the impression that it is still mutual. Despite everything. She also sees reforming Orlais as her life's work, something she must do. And she sees the throne as the means to do this. Unfortuantely the needs of the throne blinded her. But i do think she'll fight tooth and nail to try to win Briala back. After winning back the throne.
I agree there is still love there, but far too much bad blood and more than a little unhealthy dependence on the part of Celene. Think about how much of the early book lingers on how Celene doesn't sleep unless Briala is there, and how she can't start her day properly unless Briala is there to get her going, etc. and think of the poor political decisions Celene makes, that could have prevented the Civil War and which Briala urges her to make, all because sh can't give those nights/mornings up even temporarily. The relationship was based on a lie, and partially maintained through dependence. This is one of those cases where I suspect absence will make the heart grow colder, especially with Briala explicitly working to prevent Celene's victory. Which brings me to...
But more importantly... Celene may have wanted to go to Val Royeux, but Briala did not take her where Celene wanted to go. But to where she needed to be. Being stranded in the Winterpalace was not detrimental to Celene. Within a few hours she had taken back Halamshiral without a single drop of blood being shed, thus securing access to Jader and leaving her back protected.
Briala did not send her there out of spite. She sent her there because it was what actually was best for Celene.
The romantic in me would love this to be true, but the book explicitly tells us, from Briala's inner monologue, that she sends Celene to Halimshiral instead of Val Royeax specifically to prevent her from winning the war. Briala is working in direct opposition to both Celene and Gaspard, and I don't think you can add the deaths of thousands and the very real threat of losing and being executed to the list of things that make for successful reconciliation.