can you design 2-day per week strength workout for a 15 year old girl who plays soccer?

Yes—but for a 15-year-old soccer player, I’d make both weekly sessions full-body rather than split them into separate upper- and lower-body days. Resistance training can complement sports training and may improve performance while reducing injury risk; sessions should target the major muscle groups with appropriate loads and progress over time. 1 2 3

1. Day 1: Full-body session, including a squat or lunge pattern, a hip-hinge movement, and upper-body pushing and pulling. Use 2–3 work sets per exercise; select a load that allows good form and makes the set challenging without forcing failure on complex lifts. 4 5 6
2. Day 2: Repeat a full-body approach later in the week, using the same movement patterns or sensible variations. Keep the sessions manageable and allow recovery; adjust the exercise, volume, or effort if she is still fatigued. 3 7 8
3. Warm-up and exercise choices: The sources don’t provide a specific warm-up duration or a fixed soccer-specific exercise list. Choose movements she can perform safely and competently, and avoid pushing every set to failure—especially on complex lifts. 9 5

Because she is 15, have a qualified coach or strength professional supervise the program and tailor the exercises and loads to her experience and soccer schedule. 10