New Birds Quandary

Think I know what you all will say, but asking anyway 

Recently I bought 3 x 7-week old Welsummer chicks. Two died within 4 days, showing symptoms of mycoplasma. That was 4 weeks ago.
The 3rd is 110% fine - eats like a horse, lively & active, a bit mental in fact. She is 11 weeks old and about to go into a newly built house and run up the garden, by herself for now bless.
BUT - she sneezes.

Nothing wrong with her in the slightest, just sneezes. Always has. No nasal discharge, clear eyes, no gasping, growing well, perfect apart from sneezing now and again.

Now my Q........

The breeder has offered to replace the two that died, and has 2 x 8-10 week olds for me to collect at the weekend (she wasn't sure of their age offhand)

I really, really want them. But is my surviving youngster a carrier do you think, and will infect the new youngsters? I couldn't stand to watch any more die that way so soon 
She wasn't vaccinated against myco, none of the 3 were. Yet she never developed any of the secondary infections that her sisters did, which killed them.

What do you think?

Hi, I agree with hillfooter on this why oh why would you go back to that breeder after the experience you have just had with your birds. You said yourself that two died within 4 days so the breeder must have sold you infected birds, will the rest also be infected? Sorry to sound so negative but if I was you I would go elsewhere. Did you take your birds to a vets? there are many respiratory illnesses and not all are mycoplasma (mine was confirmed with a blood test - luckily she recovered and was never bred from). Joy xx