Work relationship advise

Hi, I need some advise please. I work in a small open plan office, a mix of men and women. I am 53 married and a female co-worker 30 single who I am friendly with, has lately started standing very close to me when she asks about work details. I am usually sitting and she will press her thigh against my leg, or shoulder. The last couple of times she has gently bumped me with the upper part of her thigh into my shoulder with a regular thrusting of the hips. Not sideways but slightly behind me with a forward thrusting. I am not sure, as I have never been very good at reading women other than sledgehammer tactics. Is this just flirting or have we moved to a stage where she wants more from our relationship? She also told me an earlier time that she has not had sex for over a year Could it be because I am older that she feels I am a father figure and she feels safe to flirt so heavily. I do not pull away when she touches me but I do not stand close to her and press my thigh against her when I visit her workstation. Any thoughts?