Should I get Minecraft PC, is it worth the money?

So I got some money for doing well on a test and I've been considering getting Minecraft, since I've seen so many youtubers (BlueXephos, PiinkSimmer) playing and it looks fun. I've seen the graphics, and I like them.
The game on its own (no mods), what is it like?
And with textures and mods how is it better?
Would a 14 year old girl enjoy it?
Also, is the game far better on multiplayer, since I don't have any friends who play Minecraft so will I not enjoy it if play on my own?
Finally does it require a particularly fast computer? Like would it close down or be super laggy if the computer only had just enough space on it? I don't really want to spend £18 on something that's going to be slow and laggy and shuts down a lot. Currently at this time I'm using a Windows 7 laptop, will it overheat the computer?