Those claims are incorrect.
On searching deeper, I find the clip is from a TV series, "Son of a Critch" (link).
"X" in "Xmas" stands for the Greek letter "Chi," (sometimes pronounced "Chai"), which is the first letter in the word "Christ" written in Greek, "Χριστός."
It's not "Crossing out Jesus Christ." It's NOT "Crucifying Jesus Christ again"! These fantastic claim are symptomatic of Protestants, & consigns 1500 years of English Catholicism, principally, the Sarum Rite, to the garbage!
In this clip, the actress playing "Sister Rose" also dismisses the word "Christmas," & says it should be "Christ Mass."
This is a movie or TV serial, so we are not able to get the full context from only this video clip.
However, this video clip is being spread on Social Media, with the suggestion that it is a video of an actual "catechism" or "religion" study class, and the hypothetical "Sister Rose" is dead wrong on this point too!
The English word "Christmas" is an Old English word, not a modern colloquialism, and is perfectly orthodox Catholic. It is also part of a group of similar words: Allhallowmas, Candlemas, Childermas, Christmas, Hallowmas (= Allhallowmas), Johnmas, Lammas, Martinmas, Michaelmas, Roodmas, Whitmas (= Pentecost, in Whitsuntide), etc.!
Lúcío João Mascarenhas