Is the verb generally understood by Japanese speakers? I tried searching weblio and jisho.org for レリゴる, レリゴ, or レリゴー, but couldn't get any relevant matches. Also, I tried doing a google search for レリゴる and the matches I got didn't seem to include the verb.
Jokingly coining such verb using a title/character of a movie/anime/book is not uncommon among native speakers, but many of them are one-time jokes which will be forgotten soon. Only a few of them (including マミる = to have one's head mutilated; to die a tragic death) will be widely recognized and gain specific definitions.
I don't think the verb レリゴる itself caught on last year. So the actual meaning would purely depend on the context. I think people may use it at least in three ways:
- （カラオケで）「何歌う？」「レリゴっちゃう？」 = To sing Let it Go
- （映画館の前で）「何観ようか？」「もう1回、レリゴるとか？」 = To watch Frozen
- 「まだ気にしてるの？ レリゴっちゃいなよ！」 = To let it go, to forget
EDIT: Please note that these are more like possible jokes rather than normal conversations.