Getting a colleague a thank you/valentine's card/gift?

Basically I work in an office with people older than me, I'm in my late 20s, they're mainly late 30s/40s.

Anyway as far as I'm aware they're all seeing someone apart from me and this one lady who is 20 years older than me, I do find her attractive and she's a really nice person too.

I don't drive so am one of a few who get public transport and recently she has been offering and giving me a lift to the bus after work, which is a 20 minute walk/5 minute drive. During the day we don't get much chance to talk but we are in the same office and do have to speak to each other about work-related things from time to time. She has also jokingly said if she was younger she'd go for me.

When we are in the car we discuss various things, from what we're doing at the weekend or after work to what happened during the day and just everyday things. We also recently got onto the topic of Valentine's Day and relationships, when we were talking about weekend plans and I told her I wasn't looking forward to it, she knows my last relationship broke down a few months ago and I told her how she's with someone else now.

A few days before I heard someone at work mention about someone she was seeing long distance but she said it wasn't good, was worried he was playing around and was getting fed up of it. Back in the car, I told her I'd planned to go and watch a sports event that day and she told me that she had nothing planned and said she was single, then mentioned the first time she had her heart broken, which sounded really rough, and joked that she'd been messed around by lots of guys. I told her it was their mistake and was about to say she's awesome but had to jump out of the car or else I would have missed the stop.

Anyway with Valentine's Day coming up I wondered if it would be worth getting a non-soppy, non-romantic card, was thinking a non-Valentine blank one with white flowers subtly placed in a heart shape and writing, 'Thanks for the lifts, have a wonderful Valentine's Day', obviously signing it but no mention of 'love' or anything and maybe just one small 'x' and maybe getting a small box of chocolates. What I'd hope is that she'd take it as a thank you for the lifts but also think of it as kind of a Valentine's gift and take it as a compliment and just a nice gesture. I'd also give it to her after work if she was giving me a lift, either on the Thursday evening or the Friday evening before Valentine's weekend and asking that she doesn't tell everyone.

Tl;dr: Single older lady at work has been offering me lifts to the bus after work. We chatted about Valentine's Day and how we are either not looking forward to it or have no plans. Should I get her a blank card saying thanks for the lifts and have a wonderful Valentine's Day with a small box of chocolates, saying it's a thank you for the lifts?