Splenectomy has long been a main treatment for thal intermedia because in many patients, once the spleen is removed, the destruction of red blood cells slows enough that the patients either need less frequent transfusions or no longer need transfusions at all. However, there is no way to predict if this will happen with a specific patient and some who stop transfusing will later need to resume taking blood.
I feel that the health of the spleen should be a big factor in the decision to have a splenectomy. If the patient's spleen is significantly enlarged, I feel it makes much more sense, as the enlargement is dangerous and also evidence that too many red cells are being destroyed. Many patients have improvements in health once their spleen is removed but it is a final decision as there is no putting it back once it's removed, so you must feel very sure that it is the right thing to do.
In this case, a highly respected thal doctor has recommended splenectomy. Since Dr. R.K. Marwaha, who has been a leader in using wheatgrass to raise fetal hemoglobin levels in patients, has recommended splenectomy, I would give it very serious consideration. I do not feel that Dr Marwaha would suggest this unless he felt other methods of raising hemoglobin don't offer much hope of success in raising your daughter's Hb.