This is the origin of the three dolls Marceline has. Mori basically told Hilary about what happened, which made her sad. Hilary vowed to live for her daughter, but she also didn't want her daughter to grow up without at least knowing her grandparents. Hence why Hilary made dolls.
This is what Hilary looks like after the time-skip www.zerochan.net/full/1113365
RoTG Shift belongs to
RoTG in general belongs to DreamWorks
Everything else belongs to me