Nail trimming?

[rivx]

How do you know when nail trims are needed? We've never had them done before, but I'm not exactly sure I'll know when she needs it either. They do look long. What do your 'tiels nails look like?

In the case that she needs a trimming, any tips? Are human nail clippers fine? Our local bird store does it but if I can do it at home, rather not stress her out any more than I have to. Thanks.