self fondle
Where the character in question (usually female) grabs herself for the purposes of sexual gratification. Most common targets include ass and breasts, and often accompanies masturbation or sex. Use masturbation instead if she is only grabbing her pussy (or penis, if applicable).
If a character is grabbing her breasts, but doesn't seem to be aroused (lack of blush or body/facial cues) use breast hold instead.