Is this considered boosting?

So, I recently played a bronze solo queue game with a Cait as my adc, taken this account is my (experimental) account to try things on. I was Vi jungle, but I realized how well the Cait was doing, taken she was toxic and flamed me during my leash, but she continuously got double kills on her lane "sololy". About 25-30 mins into the game, she admitted that "this is a friends account, i'm actually a diamond player". I questioned in all chat if this is allowed, because technically, she's playing for lp on another players account. Is that boosting? Or is it alright?