By Stephanie Stahl

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DELAWARE COUNTY, Pa. (CBS) — There is a special homecoming Monday for a teenager in Delaware County as she’s home from the hospital after a life-altering donation from her little sister.

Leaving the hospital is always a relief, but the discharge Monday afternoon from AI duPont Hospital for Children was extra special. Saying goodbye when you’ve been hospitalized for three months is never easy, especially when you leave wearing a mask.

And when your mom works with the local police and your dad is a paramedic, your discharge is worthy of a big celebration.

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“Thank you, this is totally unexpected,” said 17-year-old Emily Egan.

Emily was first hospitalized at AI duPont in late July. The high school senior was diagnosed with aplastic anemia, where the bone marrow stops producing blood cells.

One of the best treatment options is a bone marrow transplant and it turned out Emily’s little sister, 14-year-old Erin Egan, was a perfect match for the transplant that took place Oct. 11.

“Thank you to my wonderful family and my little sister, Erin, for giving me her bone marrow. It’s working great so far, knock on wood,” said Emily.

“Emily’s amazing and I’m glad to do what I did,” said Erin.

For the ride home, there was a limo, an escort from the Aston Police Department, and finally, back home, a warm welcome from friends and family.

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Inside, Emily is able to safely take off the protective mask and talk about how grateful she feels.

“My mind is just completely blown from this experience and my parents, they’ve been so supportive and all of their friends, thank you so much, I love you all, even if we’ve never met. I love you, you’re amazing and thank you,” said Emily.

Aplastic anemia is very rare as fewer than 1,000 people in the United States are diagnosed with it each year. Emily says she’s going back to the hospital on Halloween for a visit since she has a lot of friends there.