Most Helpful Girl
Not many guys are considered or even called pretty by female standards. This may not apply to your friend but when some girls say a guy is pretty it is usually harmless jealously. The female may wish she had an attribute that she does not naturally have. For example, I wish I had long natural eyelashes that my guy friend has (which I consider pretty).
On the otherhand, when girls call a guy pretty they may find him attractive. Overall being called pretty by females is a compliment.
Most Helpful Guy
I don't think its a lesbian thing lol. Normally its a good sign.