A man found flames shooting 13 feet into the air outside his home after he was alerted by passersby, and had to put the fire out with buckets of water.
Mold Crown Court heard that Sean White identified the arsonist who set fire to foliage outside his Wrexham house on CCTV, and immediately went out in his car to look for her.
He located the defendant Whitney Whittle, who still had a lighter in her hand.
Police arrested her at the Hurst Newton Lodge in Wrexham, where she was living at the time.
Whittle, 22, admitted arson being reckless as to whether life would be endangered following the fire at Bersham Road in Wrexham on August 31, and a similar charge following an incident the previous day when she pushed lit cardboard through the letter box of the 4th Planet Games shop in Bank Street.
Judge Rhys Rowlands jailed her for 32 months and said her actions had been very dangerous.
If the fire outside the house had not been tackled, it could have taken hold, he said.
The court heard Whittle set fire to a bush next to a bay window, but some young lads saw what she was doing and told the householder, who managed to put the fire out with buckets of water.
But the bay window was damaged along with some cabling running up the front of the house.
"If he had not known about it and that fire had taken hold, goodness knows what would have happened to the persons inside the house," said the judge.
"That is a worrying part of the case."
It had put the lives of the occupants and fire personnel at risk, he said.
The previous day, Whittle had pushed lit cardboard through the shop's letter box, but there was a fire-resistant mat inside and the fire did not take hold.
While she had a number of problems, she was not assessed as a high risk of future offending, her case did not warrant a psychiatric disposal, and there was no link between her condition and her offending, the court heard.
She was not someone who was viewed as a danger because of an obsession with fire.
Prosecuting barrister Oliver King said the defendant first tried to set fire to foliage at the front of the house, but it did not take hold and she then set fire to a bush next to the bay window at the side of the property.
"That did ignite," he said.
"The fire took hold quite quickly and passersby became concerned and alerted the householder."
The fire cracked the glass of the bay window and melted some TV cabling, he said.
Several buckets of water were used to put the fire out and the defendant was seen to walk away.
Mr White checked CCTV, got into his car and found her near the RAF Club in Ruthin Road.
She approached him and said there was a fire in Bersham, and pointed towards it, the court heard.
The defendant was holding a purple lighter in her hand, the same one that could be seen on the CCTV.
She said that there was another fire near a railway track, and she refused to give her name but said she lived at the hostel.
Whittle left across some playing fields and police arrested her at the hostel.
CCTV evidence had earlier shown her pushing lit cardboard into the shop but fortunately there was no damage.
Interviewed, she admitted what she had done, and said she picked the shop "because it was an easy target".
She did not know if there was anyone inside, had taken a cocktail of cider, beer and vodka, did not know if there was anyone in the house, and apologised for what she had done.
The defendant blamed being angry, depressed and anxious at the time.
Henry Hills, defending, said his client was a young woman of 22 of previous good character.
She had a sad background, had lost her parents at a young age and had been brought up by her grandmother.
When the time came for her to leave her care, it had precipitated a crisis, he said.
She did not have the wherewithal or inner resources to be able to cope with life in the community, said Mr Hills.
"That crisis manifested itself in these offences," he added.
Her condition meant she had difficulty comprehending the seriousness of what she had done, the court heard.
"The sad thing is that she is an extremely vulnerable individual," Mr Hills said.
He said he had written to the community mental health services which took the view that she should be subjected to a hospital order but two psychiatric reports on her showed that was not the case.
"I personally feel sad that this young woman is now having to face a period of imprisonment because there is nothing available for her," he said.
