MY SERVER IS IN DANGER NEED HELP ASAP

Hello guys my name is MewTubeTheLegend.

Ive been running a pixelmon server for a few months by now and around the past few weeks some hackers were going on and making us alot of troubles. ill leave a list of stuff they did here.

1. Hacked my friends account on enjin and destroyed my web (Was fixed)

2. This is where it gets weird, Around an hour ago someone named Chibisona came on. an old friend of mine. i soon noticed that she has spawned a pixelmon spawner (an item that spawms free pokemon) and such. i started to suspect. i made it just in time to ban her as i noticed she did /op chibisona. however the system said she left. but weird activities kept happening. i stopped the server for safety and then saw this "10.12 15:15:38 [Disconnect] User [14:50:46 INFO]: Chibisona has disconnected, reason: Server shutting down"
This is all after she was banned and saw that she left. IDK WHAT TO DO ABOUT THIS!

In this rate of the past few weeks im seriously thinking about shutting down my server because its so so soooo dangerous running a server right now. i truly need help on this...

Any help would be great. More information my server is modded MC 1.7.10. we use group manager and such.

THANKS