20 years ago or more, on an Italian channel, I saw an animated movie of a princess who falls in love with a prince and for love give her heart as a present. After that, she becomes evil, takes baths in blood and refuses to see the prince. When she dies, thorny creepers grow around the castle. The prince goes inside hurting himself to give the heart back to the dead princess and the movie ends implying he will remain buried.

IIRC the movie had a drawing similar to Disney style but with an eastern european twist (I can’t explain myself)

It’s not this one http://dvdfreak.bloudil.cz/freak.php?p=krvavapani&dz=0