Another thought.... you could confront the Pioneer™ ... say something like "Where on earth did you get such awful manners? Don't you realize that it's very poor etiquette to help yourself to other people's toiletries? And that you should bring your own when you are a guest in someone's home? Unless your host or hostess provides you with small samplers of your own, it's really rude to use toiletries that belongs to someone else unless you've asked permission first. This is someone's home, NOT a hotel."
or "Sister Pioneer™, I'm really offended that you would use something as personal as my lotion without asking first. It's very expensive, and clearly you used far more than necessary. I realize that you're on a tight budget, but so am I, and I work hard for the things I have to buy for myself. It would have been more considerate of you to ask how to use it appropriately, rather than helping yourself to an amount that would have lasted me at least a month or more. Please don't help yourself to my toiletries. I hope we never have to discuss this again because if it does happen again, I will expect you to reimburse me."
This is about personal boundaries. Once you let someone cross the line, it will be easier for them to do it again, and harder for you to put a stop to it the more it happens. Boundaries are things that you need to enforce - and sometimes loudly - in order to protect them. JWs are notorious for disrespecting other peoples' boundaries, and worming their way into your business when it is none of theirs. That's how the cult works. Boundaries are viewed as "selfish" and "prideful" and "arrogant", while allowing boundaries to be blurred and trampled over is viewed as being "self-sacrificing" and "selfless" and "unselfish" and "humility". The erosion of personal boundaries is what results in things like JW men taking liberties with young Sisters™, flirting with them and sexually harassing them, and parents not being willing to make waves because it will disrupt the "harmony" of the congregation and create bad feelings among The Friends™.
Personal boundaries are there for a reason. Don't let them be trampled. By anyone.