In diving, I believe you really get what you pay for. Unless she does ice diving, I don’t think you need to sell the farm, but there are regulators that are made special for cold water diving. Some regulators are made out of titanium to ensure longer lasting if she does a lot of salt water diving. If she only goes maybe 5 times a year, I would think a cheaper one would be fine. Anymore than that, I would suggest one a little more expensive to ensure reliability, and less maintance.