Police said the victim collapsed during the fit near the Kingfisher pub, at about 6pm on Wednesday.
But officers received reports that two men then assaulted her and stole her phone while she was incapacitated.
She was treated in hospital for injuries to her hand and knee.
A woman helped the victim following the incident, and spoke to her as she came round.
A Humberside Police spokesman said: "It’s unclear whether these were sustained when she fell or as a result of the assault."
Both men have been described as wearing blue jeans, and one was wearing a grey hoodie.
The second man was wearing a green, waxy jacket.
Anyone with infromation is asked to call police on 101, quoting Please contact us using reference 16/104172/18.