It's cute that you think that was her motivation. Now that your sperm donation to her daughter has bore fruit, you are no longer necessary and can be liquidated. Mwah-hah-hah!

If this kind of behavior is a recurring pattern of hers, you may want to have a serious talk with your wife about not allowing your MIL to visit you and the child. Her recklessness inflicted heavy bodily harm on you, and things could have been much more serious (it's not uncommon for people to die from falling down the stairs, especially if pushed with force). If she's capable of almost killing you, your child may not be safe with her. Also, it might be worth it at least to teach her a lesson about restraint and not injuring others for stupid reasons.

Press charges

She sounds horrid. Sue her to cover medical expenses and lost wages. As stated above, also press charges for assault.

I actually get it. Only the mother of a daughter who has waited to finally be a grandmother can understand, Lolol.

And what did she tell you after that? Did she realized how crazy her attitude had been? And what did your wife tell her ? Did she support you?

Ban her from your household.

You should have seen her roundhouse kick the obstetrician in the head.