I'm no expert, just a mom, but let me tell you my story. I was 26 when I conceived my son--we were kind of in the same boat, not 'trying' but not 'not trying'.
At the time of conception, I was taking Zoloft 100 mg BID (for a total of 200 mg/day) and Wellbutrin SR 150 mg BID (for a total of 300 mg/day). I also was taking Zyrtec, Singulair, Flovent, and albuterol. Since these are relatively new drugs (except albuterol), there's not much safety data on them. My OB offered to switch me to Prozac and Claritin, which are both slightly older and thus have more safety data, but I decided pregnancy was NOT the time to be screwing around with my meds. I continue to take all of these medications even while breastfeeding.
The only study I found on the safety of Zoloft was a British one done on 12 babies born to mothers taking low doses of Zoloft. The babies were a little more mellow and cried less at birth. Since the birth of my son, other data have come out recommending Zoloft for the prophylactic treatment of post-partum depression. Other studies with asthma patients have shown that babies with asthmatic mothers who do not treat their asthma appropriately during pregnancy actually tend to fare worse than the babies of mothers who do--the oxygen deprivation caused by a maternal asthma attack is much worse than the slightly increased heartrate caused by albuterol crossing the placenta.
Anyhow, I had an entirely normal pregnancy with the exception of hypertension requiring bedrest for the last three weeks--likely unrelated to the drugs. My son was--like the British study had led me to expect--an exceptionally happy newborn. He's grown into a healthy eighteen month old, and because I didn't give into paranoia during my pregnancy and instead stayed on my drugs, I'm a healthy and happy mom.
Your daughter has to decide for herself what level of risk to accept--in my case, I decided that the risk/benefit ratio was favourable and am very glad I continued my pregnancy. The thing to remember is that a certain percentage of ALL pregnancies will result in birth defects--and unfortunately, sometimes people ascribe those birth defects to drugs or to something they did or took during pregnancy, when in fact there's no relation at all.
Incidentally, while pregnant I also took Bendectin, which is vitamin B6 and doxylamine succinate (Unisom SleepTabs) for pregnancy-related nausea; Benadryl, for allergy exacerbations; and one course of methylprednisolone, for an asthma flare-up.