If you're okay with her nursing at this point, I would let her try when she asks to. It is actually fairly common for a "weaned" toddler to decide they want to nurse again at some point. Sometimes they look for comfort when going through a new developmental stage and other times they might just remember and be curious. She may actually be able to nurse occasionally at this point or she might just want to see if you will still let her. Some toddlers forget how to latch after a while and will give it up after a try or two, but its really just a matter of what you are comfortable with. If you'd rather she didn't I would just remind her that she is mommy's big girl and maybe offer to rock or cuddle with her while she drinks out of her big girl cup instead.
I noticed you said your reason for weaning was due to asthma medication. I'm curious what kind they put you on. There are several asthma meds that are safe to take while breastfeeding. I take advair & albuterol and have taken them both safely throughout my whole pregnancy and breastfeeding and my little one is just over a year. If you decide to let her try nursing again, even just once or twice a day, you might consider asking your doctor if there a safe alternative medicine you could take. Best of luck in whatever you decide!