Welcome to the board, and congratulations on the birth of that little
There aren't a lot of good guidelines for congenital thyroid disease available on the net to laypeople. But I have found one pretty good one that has info I can pass along.
Labs use age-specific references for normal ranges that are used to interpret thyroid status, and those ranges often vary among labs. Ideally, the lab will provide a reference of normal TSH and FT4 ranges for precise postnatal ages based on the specific test methods it uses. There is no one "normal" standard that all labs in the US use. You must view your baby's results in the context of the lab range used.
Normally, TSH and FT4 levels peak shortly after birth and then gradually diminish until onset of puberty, so the high TSH at birth and falling within a few days is a typical pattern. It's just that most newborns don't have TSH as high as yours did.
It isn't actually high TSH that's the problem. It's low FT4. Your baby's TSH of 7 would only be slightly high for a newborn, and it's hard to tell the status of her FT4 without the lab range used for testing... But my guess is that it's moderately lower than most newborns. If it would be severely low, she'd be having symptoms of that... poor feeding, listlessness or fussiness, general "failure to thrive". It sounds as if she is probably only slightly hypothyroid, but to be safe, that T4 should be raised by giving her supplemental hormone.
My source says that babies can be transiently hypothyroid if their mothers are hypothyroid. If mom is not, then the hypoT is more likely to be permanent. In either case, it's best to start treatment and continue it steadily for at least 2-3 years, after which the need for it can be re-evaluated.
I feel sure that sweetie will be just fine with good medical care and your love.