I really liked her! I wish they'd kept her longer on the show, I actually liked the idea of having a trio of detectives. Plus her relationship with Sherlock was really well written. His relationship with Oscar, instead, was an absolute mess: instead of 'show, don't tell', they kept insisting and insisting that he was a huge influence on Sherlock, but nothing in the character or in their interactions showed that at all. Really bad writing there.