My girlfriend expects me to share my inheritance even though we've only dated 8 months

My grandfather passed away last month and left me $50,000. My girlfriend and I have been together 8 months.

She's now talking about "our inheritance" and making plans for how "we" should spend it. I said this is MY inheritance.

She got upset saying "I thought we were partners?" I said we are but we've been together less than a year!

She's made a whole budget showing how "we" should use the money - paying off her student loans, down payment on "our" first home, vacation for "us."

I said I'm using it for MY student loans and savings. She said "You're being really selfish about this. Don't you see us having a future?"

I do see a future but that doesn't mean my inheritance before marriage becomes joint property! She says "If you really loved me you'd want to share everything."

She's given me an ultimatum - agree to split the inheritance and use it for "our life together" or she's "reconsidering the relationship."

I told her that's financial manipulation. She said "It's called being committed!"

We don't even live together! We've never talked about marriage! Why does she think she's entitled to money my grandfather left specifically to me??

I'm seriously considering ending things because this showed me a side of her I don't like.