There's nothing wrong with wearing lip liner. It has two functions: to keep the lipstick from feathering or bleeding, and to make your lips look bigger. However, many women make the mistake of wearing a lip liner that's much darker than their shade of lipstick. This was briefly a trend in the 1990s, but we mean briefly.
Also, sporting a dark outline of lip liner in contrast to a lighter lipstick will give you an odd ring-around-the-mouth appearance, which is simply not an attractive look. Use a lip liner that matches or closely complements your lipstick, or try a clear lip liner. For older women, a clear lip liner is best, because it won't noticeably settle into lines around the mouth as the day goes on.