I've known this person online for around 6 months and she is going homeless and needs money. Should I give this person some money?
There's a lot to think about here. Six months can be a long time, but it would depend upon how you define the word "know." I would also consider the circumstances of how a person got into whatever situation they were in. You don't want to be enabling people with addictions or layabouts. It also depends upon whether or not you, yourself, can afford it and what you would be doing with the money if you didn't give it away.
I am generally suspicious of internet sob stories, but I am also a cantankerous old bastard (ask anyone). Most people are nicer than me, so my advice may not be helpful, but I suspect your heart will tell you what to do. Hearts are not always correct in their judgment, but neither are heads, and following your heart will make you feel like you did the right thing no matter what actually happens.