Claire Roundill, 32, from Hull, sent the 15-year-old boy naked pictures of herself before having sex in her car. At the same time she was having a relationship with his older brother. She became pregnant and admitted she did not know which teenage boy was the father.
She was spared jail yesterday after pleading guilty to sexual activity with a child, supplying cannabis and possession of the drug at Hull Crown Court.
She claimed she was initially unaware of the schoolboy's age - nevertheless she had sex with him again when she knew he was under the age of consent.
Prosecutor Jharna Jobes said Roundill sent the younger brother text messages, asking to meet up, and sent him pictures of her naked breasts. She also supplied the schoolboy with cannabis.
The court heard that Roundill had an abortion after discovering she was pregnant.
The 15-year-old boy said Roundill bombarded him with hundreds of text messages and photographs every day.
He said: "She would be in sexy outfits or topless. I now know she took advantage of me. I just want to put it behind me."
Roundill's barrister Charlotte Baines said: "She accepts she had sex with him a second time in the knowledge he was just short of his 16th birthday. There was some sort of relationship between the two of them. She openly admits she had cannabis at her house."
Ms Baines added Roundill was having 'a difficult time' in her life when she embarked on the relationships.
She said: "She was suffering financially and her marriage was in real trouble. She is not the type of defendant the court needs to send to prison immediately."
Roundill was given a nine-month prison sentence, suspended for two years. She must also sign the Sex Offenders' Register for 10 years.
Judge John Dowse told her: "The court must mark its displeasure at this offence. You now have a criminal record for the rest of your life.
He added: "It is not suggested you are a bad mother but you threw into risk, by your conduct, the prospect of caring for and looking after your own children.
"I recognise you have had an unhappy life over the last two to three years.
"Equally, I recognise there has been a victim personal statement from the boy which says he wants to put all this behind him and he is relieved that he does not have to give evidence in this case."
The father of the two teenage boys, who cannot be named for legal reasons, has said Roundhill's sentence was too lenient.
He said: "If it had been the other way around and this was a man having sex with a 15-year-old girl, he would have been locked up, without a shadow of a doubt. But, because she is a woman, she has walked free.
"She took advantage of both my sons. When my elder son dumped her, she targeted the younger. She planned it. I hope she now realises exactly what she has done.
"If she had gone to prison, I would have been happy but she has just got a slap on the wrist. We are disappointed. This doesn't send out a message.
"Before this, he was a lovely boy and now it has changed him. He has gone off the rails. He has been in trouble with the police and this has never happened before.
"It was disgusting what she did. She has taken advantage of my family. If we had known what was going on, we would have put a stop to it straight away."