Trump account retweets incendiary videos
This was followed by two more videos of people Ms Fransen claims to be Muslim.
Britain First was founded in 2011 by former members of the far-right British National Party (BNP).
The group has grabbed attention on social media with controversial posts about what they deem "the Islamification of the UK".
It has put up members to run in general elections on anti-immigration and anti-abortion policies, but has yet to secure any seats.
A history of Trump on Twitter
Ms Fransen has more than 52,000 followers on Twitter.
She responded enthusiastically to Mr Trump sharing her tweets. She posted on her account: "Donald Trump himself has retweeted these videos and has around 44 million followers!"
"God bless you Trump! God bless America!," she added.
The original video was shared by US conservative commentator Ann Coulter who Mr Trump follows.