It is an unnecessary variant for a "fear of being left alone, abandoned or rejected" that has already been baptized with more or less success as autophobia, monophobia or eremophobia, which are all Greek words. The problem with 'isolophobia' is that it looks like a Spanish version of the English isolophobia for isolated phobia, which eventually comes from the Latin insulatus, a, um (isolated, alone, abandoned) and does not justify the hodgepodge with the suffix -phobia which is Greek.