What does this tweet mean? "Never gonna happen. Two completely different worlds. I need to give up"?

[Mr.foofoo]

A girl on Twitter tweeted this. If anyone can help me interpret this. What was she referring to?

[Xuan :D]

She probably means that she has a crush on someone but he's too 'far away' from him in terms of standards. Like he's too good for her or she's too good for him.
She's trying to stop liking him I guess, when she said 'I need to give up'. She thinks it's hopeless

[Ron]

guessing the two worlds means there is a big age difference, she might be still in school, he well into his career

[KatelynChance]

She's a Doctor Who fangirl who wants the Doctor, which is never going to happen because she's from Earth while he's from Gallifrey. It's just her way of acknowledging that timelord-human relationships will never work.