When details at the time of christening were temporarily written down to some paper, errors in names appeared, when later recorded to the book. Or complete omissions, if he notes were lost for some reason. It's only human.
That's why genealogy researchers need to follow all he records available, as you apparently have done. Too often beginners pick some birth that is close to the later records.
There is no doubt that Ulrica belongs to the family of Greta and her first husband, as otherwise listed in HisKi:
*28.10.1795 1.11.1795 Alaj. Skrabb Eric Johansson Margeta Ericsdr. Maria
*27.2.1798 28.2.1798 Alaj. Skrabb Eric Joh:s. Greta Ersdr. Henric
*10.8.1799 16.8.1799 Alaj. Skrabb Eric Johansson Greta Ersdr. Johan
*28.9.1800 5.10.1800 Alaj. Skrabb Eric Johansson Greta Ersdr. Susan:a
*21.3.1803 25.3.1803 Alaj. Skrabb Eric Joh:son Greta Ersdr. Eric
*8.6.1804 10.6.1804 Alaj. Skrabb Eric Johanss. Greta Ersdr Johan
*9.6.1805 10.6.1805 Alaj. Skrabb Eric Johss. Greta Ersdr Jacob
*28.7.1806 3.8.1806 Alaj. Njemitalo Erik Johans. Greta Eriksd Mats
*7.6.1808 12.6.1808 Alaj. Niemitalå Eric Johs. Greta Ersd Gustaf
*14.10.1811 20.10.1811 Alaj. Njemitalå Eric Johs. Greta Ersd Anders
*16.12.1812 20.12.1812 Alaj. Skrabb Eric Johs. Greta Ersd Helena
*10.7.1814 10.7.1814 Alaj. Skrabb Eric Johs. Marg. Eriksd Eric

Jaska
P:S. Tuula K already replied while I was typing.