Solo strength training works for self-motivated people. Training with a partner improves consistency (harder to skip), form (spot each other), and confidence on heavier lifts (spotter available). Particularly useful for big compound lifts where solo attempts of maximum weight can be risky.
What partner training enables
Heavier sets you wouldn't attempt alone. Form feedback between sets. Motivation to show up consistently. Sometimes-friendly competition that improves both partners.
How to find one
Existing gym goer of similar level. Friend or partner you can convince to start. Online groups (Strong Women UK Facebook groups, local lifting communities). Mismatched partners (very different levels or goals) usually don't work long-term.
Even one partnered session per week alongside solo sessions improves outcomes significantly for most lifters.