The word latter is used to indicate which person it is referring to. If, for example, you list two names the first name would be the former and the second name would be the latter. So you could restate this sentence as "Demi Lovato has seemingly offered her support to Selena Gomez, following Selena's recent time in rehab".

"the former" and "the latter" are used when you are talking about two concepts, things, or people in a sentence. "The former" refers to the first thing/person and "the latter" refers to the second concept/thing/person. These phrases are used to avoid repetition of the same name for a concept/object/person. For example, the meaning in the above sentence is: "Demi Lovato has seemingly offered her support to Selena Gomez, following Selena Gomez's recent time in rehab." In English, we avoid repeating the same name twice in a sentence. So "Selena Gomez" is replaced by "the latter." You could use "the former" in this sentence as well: "Demi Lovato has seemingly offered her support to Selena Gomez, but people are suspicious due to the former's habit of catty comments." I hope this helped!

In general "latter" can mean the more recent, the one, or ones closer to the end than the beginning. It is not always restricted to 1 of 2 option. The latter half of the year.... The latter months of the year see a warming of the weather.