An attention whore is
(Internet, slang, derogatory) Someone who craves attention and is not above soliciting it via deliberately meaningless or provocative tactics.
This is not related to a hoard, or the act of hoarding ("To amass, usually for one's personal collection"), nor do the two terms share a root.
However, it's easy to see how attention whore or the novel term baby whore come from the word whore. The key parts of the definition:
(pejorative) A person who is considered to be sexually promiscuous.
A person who is unscrupulous, especially one who compromises their principles for gain.
An attention whore is indiscriminate about the source of the attention, and perhaps is a sellout who doesn't care how they draw the eye.
In your example, when someone is called a baby whore, it is a mildly derogatory statement, fairly nonsensical, but a joking put-down perhaps suggesting that one must like all babies. Using whore or slut in this way often brings in the idea of not being choosy when one should be (this is probably why it made you think of the idea of hoarding) or of liking something when a "good" person would not, particularly if it were an obligation.
Such derogatory words for women are often used this way, either as a genuine pejorative (attention whore is not so friendly in many uses), or with a humorous or satirical intent. Consider one friend to another: Hey, code bitch, get back to work. or,
What a camera slut! He's in photos with everyone.