Illaoi damage bug? [gameplay]

I just played an ARAM match against illaoi and somehow she was regularly doing 2550+ true damage to me as rammus. This would happen just after breaking tether with my ghost and she did it repeatedly. She was also doing it to other team mates and could nearly solo our team because of it. I'm talking 1-shots on the reg. The worst part was that she was built completely tanky, so she had as much hp/mr/armor as i did.

What the actual fuck?