Hi Dianna.
Welcome to our site .I hope we can be of need to you.
I feel compel to answer your question and may be ease your doubt about the above topic.
First thing I would like to be, that perfectly imperfect child in the orphange, waiting for that perfectly imperfect parents to adopt me.We all need love, nurture and acceptance to thrive.I made this point because we are all perfectly imperfect.No one here, will be able to tell you how much it will cost to raise a child with Thalasemia as we are all individual with individual needs.It all depand upon whether you and your husband both love this child and you both can afford to give her the best she deserve , only both of you knows that.
In regard to your other child I dont thing she will get infected, maybe jealous if you spent most of your time with the sick one, but on the other hand he or she might be gratefull to have a sibbling, again I stress it is how we deal with our issues, each one of us knows what is best for us .
Please remember this child is as good as the next one, its not his or her fault if she was born with a genetic disorder.I hope you are brave and have the guts to think outside the box because that what's take to accept what we cannot change.I will pray you both have proper guidance .
As a matter of fact, this is solely my point of view ,maybe some other members have a different view and can also help you find peace of mind on this subject and make the right choice.
Kathy.