A Reiki master asked if I'd had an abortion (I've not)...what can cause similar damage/blocks to chakras?

That was very irresponsible and unprofessional of her to ask such a question. She should have asked some general questions regarding the nature of the chakra in question. The sacral chakra (spleen is a meridian, not a chakra) is, among other things, in charge of our emotional relationships with others and our uality. So she should have asked some general questions along those lines and listened to whatever you felt comfortable disclosing to her.