“My brother died and his girlfriend is all over me”

My brother died and we just had his funeral, but during it, his girlfriend was overly touchy-feely with me. During hugs she would be squeezing my arms and back. During a sit down hug she was grabbing my head and kissing me all over.

It would be different if I was a kid or something, but I’m 20 years old. I’ve only met her once before all this and didn’t think anything of it. Now she is inviting me out to coffee and I’d rather not. How do I politely decline and make sure I never see her again?