Custom integration into other plugin

Hi, I only have basic PHP skills. I managed to integrate this captcha plugin into the form of another plugin. I therefore created two hooks in my child themes functions.php that hook into the plugins “form” function “check” function. Everything works fine except I am currently using $captcha_instance = new ReallySimpleCaptcha(); in both hooks and of course that leads to the creation of two different instances. How can I correct/bypass this?
Many thanks!! Hannes