Currently in India, Rivas was spending her first Christmas without her daughters Luna, six, and Isla, four.
The former WAG claimed she attempted to speak to her girls on the phone to wish them a 'happy Christmas', but Lampard wouldn't allow her.
Clearly upset, she then blasted the England footballer on Twitter, then brought his fiancée Christine Bleakley, the Dancing on Ice presenter, into the argument.
She wrote on Christmas Eve: ''You would have thought the girlfriend would have a little maternal understanding...'
Bleakley must have been alerted to Rivas' claims and re-tweeted a comment from a friend Jill Morgan which said: 'Looks like someone is up to their old tricks again, telling lies!! Have an amazing Xmas @clbleakley with frank & the girls! C u nxt wk xxxx.'
The former Daybreak host then explained: 'Thanks J. I'd happily put the record straight but really don't think twitter is a place to do it when children are involved x.'
Despite claiming she didn't want to get involved, Bleakley retweeted other comments from followers suggesting 'a dignified silence' was the best way to deal with the situation.
When another follower accused Rivas of having 'no class and sour grapes', Bleakley replied: 'Your words are much appreciated.'
She then retweeted another comment from Deirdre Hogan, reading: 'What mother would leave her kids at Christmas in the first instance. They lucky to have Christine.'
The plot thickened when Gavin Henson, ex-fiance of Charlotte Church, weighed in with a message to Bleakley: "furthermore very spiteful to tweet comments like someones elses children are very "lucky" to have you..... how modest christine"
According to her Twitter page, Rivas is in New Delhi, India for Christmas after leaving the UK on December 16.
Rivas and Lampard have shared custody of their two daughters since splitting in November 2008 after seven years together. Bleakley became engaged to the Chelsea footballer in June this year.
Ouch! Should grown-ups be spatting like this in public about children?