RE: constipation. All formulas have iron in them. Check the amounts because iron can easily constipate people.
Also look at every teat in the shop. Pick the one that closely resembles your nipple shape post feed. My niece likes Tommy Tippee Nuby, my LO likes Mam ultivent.
Don,t have it too warm or too cold as it sort of surprises them at first.
Also my LO soon sussed what time she could have breast milk again but didn,t refuse it too much during the day.
Oh and....Don,t forget that it takes longer for them to digest so they do lose the comfort part of B/F. It does not harm them but extra hugs may be required.
Erm...........thats all I can think of, hope it helps you, good luck
p.s you could test her with a sneaky formula dream feed to see if she actually notices the difference in taste!