I have the perfect answer for you since I literally just solved the issue myself.
First of all make sure meteor works in the default windows command prompt. Next open git bash and check if the following command works:
cmd //c meteor
This runs the command meteor as if you were in the command prompt.
Next step is to set up an alias in git bash so you don’t have to type that out each time.
Open git bash and enter the following:
vim ~/.bashrc
this will open/create the bashrc file in VIM, press i to insert and type the following:
alias meteor="cmd //c meteor"
Save and exit vim by first pressing the Esc key then press the “:” key. Now you should be able to enter commands in VIM. Type “wq” and press enter which will write into your .bashrc file and exit vim.
Almost there! Now that you are back in git bash, all you need to do is point to your .bashrc file by entering the following:
source ~/.bashrc
Now you will be able to run meteor commands straight from git bash! Hope that helped!