If the only way she can eat is to lick it off your finger, then she will have to interact with you. Decide how much she should eat in a day, get fishy flavored canned and give it to her in little bits off your finger several times a day. Talk softly to her and use her name a lot as she eats, so that word becomes associated with pleasure. Don't try to pet her too soon; especially head pets terrify feral cats. (You can switch her to dry food later if that's what you usually use...with sme canned mixed in, the change will be easy)