meaning of "take the worst yourself"

Solution 1:

It’s just extending Charles’s joke.

Jane tells Cassandra that Charles sends his love, but with a distinction: “best love” to Cassandra herself, “worst love” to Edward. This is a joke because generally one sends “love” or “best love”. There isn’t such a thing as “worst love”—the phrase is oxymoronic. But if one has a teasing relationship with a sibling or other family member, one could tease that person by saying “I send you love. Not good love, just my worst love.”

That’s what Charles does to Edward. But since the letter is to Cassandra and not to Edward directly, he tells Jane to tell Cassandra that if she does not want to tell Edward that Charles sends him his “worst love” because she might consider such teasing improper, then Cassandra herself can keep the “worst love” and let Edward have the best that he (Charles) had sent to Cassandra.