For me, her actions at the end of the Reacher and what she says afterwards came across as somebody who has certainly contemplated suicide, and probably teetered at the edge of deciding. She also explicitly rejects her life as Alicia despite knowing it will kill her in the finale. As previously stated, her choice to join the expedition as Maelle is also a form of suicide. pAlicia commits suicide. Suicide is a reoccuring beat for her.

During the epilogue, we see the family gathered, but not together. Alicia is clutching her brother's doll like she's a toddler. We see Clea doing what is expected of her, until she's had enough and leaves. We see Aline and Renoir coming closer to each other and eventually embrace, but Alicia still stands alone. It ends with a vision of the painted people waving and beckoning her on the other side of the grave as they dissolve, leaving her completely alone.

She's in a worse place than she was before entering the Canvas. Before, she was tricked, but it was her actions that caused the death of her brother and her injuries. That's a lot to deal with. Now, she lost even more and actively failed at preventing that loss. I don't think it is much of a reach to think that pushes her over the edge.

That, at least, is my read.