I don't want to move closer to my significant other's cancer-stricken parents.
Why don't you want to support your partner and move closer to her parents?
Because my girlfriend's parents can influence my marriage decision negatively.
It's understandable that you want to prevent a negative influence on your marriage. However, you should support your significant other during this difficult time and talk to her about your concerns.
You are not understanding what I'm saying. I can't support my girlfriend during this time since I will do things I regret if I stay there.
I can understand, but you should support your partner in their time of need. It's expected that you should communicate to them how you feel. Maybe a compromise can be made and you can find ways to address your attitude.