A toddler has gone viral for the sweet moment in which she comforted her pregnant mom who's been struggling with morning sickness. 

Katherine Hagen, 32, is an expectant mother from St. Louis, Missouri.

She's been struggling with morning sickness since very early on in this pregnancy. 

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Hagen is already mom of 2½-year-old Rosie, who's been warming hearts through a social media video.

In the video, little Rosie Hagen can be seen comforting her mom during her bout with morning sickness. (SEE the video at the top of this article.)

The 38-week pregnant mom spoke with Fox News Digital about her daughter’s "sweet and enduring" personality. 

"She is a very funny kid who likes to make people laugh — she’s also pretty spunky and never stops talking," she said. 

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The soon-to-be mother of two shared that her daughter is always on the lookout for when she runs to the bathroom to deal with morning sickness. 

"She will usually state, ‘Mom’s puking,’ and then run after me to the bathroom because she insists on rubbing my back, repeatedly tells me, ‘It’s OK,’ and then flushing the toilet when I’m done," she said. 

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Hagen said her morning sickness started early on in her pregnancy and has still frequently made an appearance even late into her third trimester. 

"Sometimes she [Rosie Hagen] will even pretend to be sick herself and tell us that she’s going to puke — and then yells from the bathroom, ‘Will you rub my back?’ as she pretends to throw up in the toilet," the mom said. 

Hagen said she doesn’t think her daughter fully understands that she will have a baby brother soon — but she's been by her mom’s side throughout the entire pregnancy. 

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"She insists on putting lotion on her belly because she has seen me do it throughout my pregnancy," she said. 

Hagen told Fox News Digital that she thinks Rosie Hagen will be the best big sister in tending to her baby brother’s needs — something she is proud of as a parent. 

"To see her be so empathetic and caring at such a young age makes me feel like we’re doing something right as her parents," she said. 

Hagen shared that one of Rosie Hagen’s favorite songs is "Anti-Hero" by Taylor Swift — and that she loves Reggie, her Goldendoodle.