She doesn't know if she's really interested

M25 I'm dating an old friend of mine F25. After the third date she told me that she still doesn't know if she's really interested or simply that she likes my presence. However she wants to take it slow. We kissed, but I receive mixed signals (she's happy, but maybe not into me in that way). I told her I like her very much and that I will wait and leave her space. What should I do?