Hi Becki24 and welcome to Pearl Guide!
What a lovely idea, wearing your mother's pearls at your wedding. They look like they might be akoya pearls, but I'm wondering if your mother added the two pearls that don't match the others. They are symmetrically placed, and they ease the graduation, which makes me think that is possible.
You could restring the necklace, omitting those two if you want it to look more uniform in color. This would also eliminate the gap between two of the pearls, and make it easier to find earrings to match the color of the necklace as a whole. Restringing as a good idea anyway because silk becomes weak and breakage is a risk.
Older pearls can become yellowed or cream colored and sometimes it's difficult to match them as newer pearls may be whiter. If you find this to be the case, you might want to check out local shops that sell estate jewelry for matching earrings.