I think infertility is extremely complicated with so many factors influencing it - environmental, diet, physicial, emotional, and many others. There are a lot of risks with plastic that we use too much of anyway. Certainly environmental groups are trying to educate people not to use bottled water, for many reasons. When the water that comes out of the tap is generally very safe, it hardly makes sense to use plactic bottles made of petroleum products which are then filled with municipal water from another city, or possibly spring water (which has bacteria and may or may not be regulated in any way), then put that bottle on a truck which burns oil to drive across half the country, with the bottle maybe getting very hot in the sun only to sit in a warehouse so it can be shipped to a supermarket, where you burn oil to go purchase it and bring it home. Then you use more gas to take it to the recycling center or have the recycling truck pick it up -- well, that doesn't make sense on a lot of levels.
However, it's very difficult to blame infertility on the bottle - you don't know if the infertility has to do with her body, the husband's body, or some combination. There are probably a million things she can do to improve her health and her chances of getting pregnant, but we don't really know what she's already doing and what any tests have shown. It's probably wise to stop using the bottles but not specifically because of infertility. As someone who battled infertility, I have to say that it was SO HARD to hear comments from people about what was causing it. The worst was, "Just RELAX! My friend XYZ stopped worrying & trying, and bingo, she got pregnant immediately." Like I was causing my own problem! It's never just one little thing that can be done - and it has to be her choice whether she undergoes evaluations and tests and starts eliminating certain things from her lifestyle. She probably already feels terrible about not getting pregnant - I know I did, and it's very lonely and isolating and frustrating - but there's no direct, immediate and definite link between the water bottle and the infertility. It's really hard to get blamed for causing your own problem, when your actions may not be responsible for it at all.
They are certainly changing the types of plastics in bottles because of cancer worries, and of course the environmental issue is huge. I think all you can do is make every effort to NOT do things in your own life that affect your health or the health of others, and share stories that help to educate everyone. Getting involved in an environmental group is a great thing, not just because of the people who will listen to you, but because of the tremendous work you will be doing and the great people you will meet who know even more things than you do - what a great way to educate each other!
You obviously care a great deal - I think the best way to use that care and concern is to direct it into a reputable organization that can have an impact on people, their practices, and public policy.