I don't know about contacting senator. But I think you should definitely ask her to mention the baby. Family milestones such as arrival of a new baby and your mother in law coming over to visit her grandchild is worth mentioning so that they understand it's more than tourism.
Has she travelled to other countries requiring a visa recently? What are her ties to the Ukraine--pension, property, family members, does not speak English? SHE must show that SHE will return to the Ukraine after her visit. The CO only has the evidence submitted to determine that and will probably take all of 15 minutes to decide. The default response for a tourist visa is DENIED as all CO think the applicant--i.e. your MIL--is going to use the tourist visa to enter the US and remain. She needs to overcome that assumption and with a daughter and now a grandchild in the US it will be a bit harder. You do not know unless she tries and it will cost $165 to make each attempt. Every family member that wants to visit us in the US has to go thru the same process. Some get approved without any problems and other get refused. It is frustrating, but that is the game we entered into by marrying someone from another country. At least a tourist visa for citizens of Kazakhstan are getting easier to obtain--by easier I mean less refusals--but given the situation in the Ukraine, she may have a hard time getting a tourist visa--just want you and your wife to be prepared that the only way for her mother to see the new grandchild is to fly to the Ukraine.
Good luck,
Dave
