Samantha Jayne Jones, 25, burst into tears and said she was a changed woman after she pleaded guilty to forgery, uttering, family violence order breach, fire damage and assault charges.

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To get a birth certificate in January 2016, Jones admitted she used the driver's licence of a man who "walked out" on her while she was pregnant.

"Yes he was none the wiser, yes I did sign it, but my intention... was not to gain anything financial from that," Jones said in Launceston Magistrates Court on Thursday.

Jones' crime only came to light after the man whose signature she forged saw the birth certificate and contacted police years later.

Another man Jones targeted in January this year had his left knee stabbed after he refused to sit down for Jones during a dispute.

Jones threatened to stab the man again if he didn't do what he was told, jumped on the bonnet of his car and pulled off an aerial.

After Jones and the man got in a car together she threatened to jump out while it was moving. The man slammed on the brakes and Jones scratched him.

In February, the same pair had an argument and Jones threw the man's work uniform on the ground outside a house and used a lit cigarette to set fire to the clothes.

Magistrate Ken Stanton said Jones tried to exert power and control over the man, and she needed to serve a term of imprisonment.

"This is your seventh and eighth charge of common assault," Mr Stanton told Jones.

When the potential jail stint was mentioned, Jones said she was turning her life around.

"I am changing for the better, I don't want to go to prison, I don't want to be back here," she said.

Mr Stanton sentenced Jones to a six-week prison term, which was wholly suspended for 12 months. Jones was also fined $500 and given a 12-month community corrections order.