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Top picks: Metal Planet Ltd 21st Birthday Metal Key (best overall); VOSAP Heart Cubic Zirconia Infinity Necklace if she wears a necklace every day; Funistree Candle Warmer Lamp with Timer Dimmer if she loves scented candles.
A 21st is the birthday with its own symbol, the key, so this is the year to give her something she keeps rather than uses up. Under £30, choose between a piece for her shelf, a piece to wear, or one small comfort for the flat or room she now runs herself.
The Metal Planet Ltd key is solid metal with sparkly crystal stones set inside the 21, tied to a Happy 21st Birthday card in a presentation box. It is designed and made at the brand's Hertfordshire studios.
Worth knowing: Skip if she would rather have something to wear than display.
The VOSAP necklace has an infinity pendant set with a cubic zirconia heart, and it arrives in a keepsake box with a 21st birthday card.
Worth knowing: Skip if she only wears sterling silver.
The Funistree lamp melts a jar candle from above without lighting the wick, so there is no open flame in her room. Its timer switches it off by itself.
Worth knowing: Skip if she does not burn jar candles.
The ALBISS mug is pink marble-effect ceramic with gold print, and comes with a lid, spoon and greeting card in a gift box, ready for her 21st.
Worth knowing: Skip if she only drinks from a travel cup.
The KIUEZIR set gives her a floral rhinestone tiara and an "It's my 21 birthday" glitter sash to wear on the night. The tiara has combs on each side to hold it in place.
Worth knowing: Skip if she prefers a low-key birthday.
The Kideerly crochet star holds a small sign reading "The world shines brighter with you in it, Happy 21st Birthday", and comes with a greeting card.
Worth knowing: Skip if she does not keep soft ornaments.