Feiya

Well, in DnD 5e there is only one black tentacle spell (that I know of) and that's Evard's Black Tentacles, which restrain and deal damage not really a great idea, especially since it is also a concentration spell, so unless she has the Warcaster Feat she is going to probably lose those tentacles pretty soon.

I do wish that Warlocks had an evocation that made them immune to the effects of Evard's Black Tentacles, combine that with Eldritch Blast and the Grasp of Hadar evocation and you would be set. Just grab enemies pull them in and laugh as they are restrained and take damage.