It is not safe! I worked as a Materniry nurse for 5 year and we always advised our patients AGAINST taking sunbeds. Use fake tan instead, it's sooooooo much safer for you!!!!!
Why don't you phone NHS Direct or ask at a pharmacy or your own doctor's surgery for advice, not sure if anyone on this site is suitably qualified to answer it properly. I know that X-rays are bad for pregnant women and that the hospitals do not like to scan women too often because of the risks, similarly I have read that computer equipment MAY be bad too (a certain type of radiation given off?). I also know that heat is bad for unborn babies like in hot baths and jacuzzies.
Please ask someone for the definitive answer, although if sunbeds are harmful, the first 12 weeks are the most important to get through safely, in my experience. Hope she's lucky enough not to have harmed the baby.
You shouldn't be using sunbeds any due to skin cancer reasons. But specially when you are pregnant. The safest thing to do may seem really obvious but go down to your local salon and then get a spray tan!
Good Luck
xXx