The claim that Easter is a christianised festival of a pagan goddess is asserted with far more confidence than the evidence supports, and the evidence can be quoted in full because there is one sentence of it.
Bede, writing De Temporum Ratione in 725, is explaining the old English month names. He says that Eosturmonath has a name now translated as the paschal month, and was once called after a goddess of theirs named Eostre, in whose honour feasts were celebrated in that month. That is the entire testimony. He also names a goddess Hretha for the preceding month, about whom nothing else is known either.
Bede does not mention eggs, hares, spring rites, a festival of any described content, or any connection between her worship and the Christian feast beyond the name of the month.
Whether the goddess existed at all was disputed for a century, with some scholars arguing Bede inferred her from the month name. The discovery in 1958 near Morken-Harff in Germany of over a hundred and fifty Romano-Germanic votive inscriptions to the matronae Austriahenae supplied linguistic support for a divine name of that root, and most specialists now accept that Bede was reporting something rather than inventing it. Philip Shaw has argued she was a local goddess of a particular region rather than a pan-Germanic one.
So: the goddess is probably real, and Bede's month name is genuine. Everything else, the derivation of the feast, the eggs, the hares, the rabbit, is later inference or nineteenth-century speculation, much of it from Jacob Grimm. Note also that most European languages call the feast some form of Pascha, from Pesach. Only English and German use the Eostre root at all.