Years ago, one of my best friends asked me to make her curtains. I told her if she got the pattern, I'd teach her how. I'd do one side, she, the other. We did. Since then we've made many things. Same rule applied. As women do, we stitch and bitch each time we make something.
If she had been just a neighbor or acquaintance, I would tell her where we go for alterations...and not hem her pants. I probably would have told her where she could find a JoAnn's coupon, not given her mine. Unless I was sure I wouldn't use it.
The fact that she knew there were other means of decreasing the length of her pants, seems a bit odd to me. I'm sure she knows where she can get them altered and didn't want to spend any (or that much) money!