When a another woman buys your boyfriend a sexual present?

As with most things in life honesty is the best policy. If you aren't comfortable with your man getting dirty gifts for other women tell him so. It maybe some harmless fun or she may have eyes for him, try establish if he is interested in her. This will be difficult 'cos most guys lie like flat fishes when it comes to this sort of thing.

One more thing to think about: is the gift intended for use by couples or masturbation If it's for both of you maybe she's trying to spice up your sex life. If it's just for him she's probably implying that he's a wanker.