Juliet is feeling a mixture of fear, desperation, and determination before she drinks the vial of liquid because she is afraid of marrying Paris, desperate to be with Romeo, and determined to take control of her own fate.
Shakespeare describes her feeling very well just before she drinks it. She tells the nurse goodby and thinks about her life.
Juliet's Nurse
In her soliloquy before drinking the potion, Juliet does not express regret over her love for Romeo. She is instead focused on finding a way to be with him despite the obstacles in their path.
Nothing about Romeo and Juliet is real. It's a play. It's all make-believe.
Friar Laurence tells Juliet that she will appear dead for 42 hours after she drinks the potion, and then she will wake up as if from a pleasant sleep.
He drinks poison, in Juliet tomb to "die with her", thinking Juliet was really dead. And Juliet stabbs herself when she see Romeo dead.
In the play, Romeo last sees Juliet in the tomb, and thinking that she is dead, he drinks poison.
He drinks the poison.
Romeo hears that Juliet has died although she has only faked it and so he buys a poison from a poor apothecary and drinks it by her side seconds before she wakes again.
Romeo's dagger, right after Romeo drinks the poison.
That she will be in a coma for two days.
Juliet says, "Romeo, I come! This do I drink to thee!" and she drinks Friar Lawrence's potion.