With a glassy countenance Did she look to Camelot. (lines 130-131)
Sadly, even once she gets out of her prison/bower, the Lady is still isolated. We really feel it in this moment, as she looks down the river and sees her doom. She can feel the weight of the curse, and she knows she won't make it to Camelot, at least not alive. One of the things this poem might make us wonder is whether it's the physical isolation that's the problem or some kind of deeper loneliness inside. In general, the inside vs. the outside is a big and complicated theme in this poem.
Singing in her song she died, (line 152)
Ultimately, she dies alone. She might have achieved a kind of freedom at the end, but the Lady remains isolated through the whole poem. We get a lot of little hints about this. For example, she dies in a boat, which separates her from the river and the world – it's like a little coffin. Also, check out the way this line says she died "in" her song. That's a funny way of saying it, and gives us the feeling that she was somehow a prisoner in her lonely song too. Sorry, that sounds pretty grim doesn't it? This is not the happiest poem.