A 20-year-old Lowell woman is on probation with a suspended sentence of 14 months in jail after pleading guilty to charges of assault and battery with a dangerous weapon. The charges against Alyssa Coughlin stem from an incident in June in which she and several friends arrived uninvited to a house party and refused to leave. Originally a small gathering to welcome home a returning Marine, the party was invaded by dozens of crashers. Words were exchanged before the standoff became violent. Coughlin and several friends attacked the hostess of the party, who sustained facial injuries. While on probation, Coughlin was ordered to undergo substance evaluation and treatment and to complete 50 hours of community service.