Consider the following major STDs: HIV, chlamydia, syphilis, gonorrhea, Hepatitis B & C and Genital Herpes.
I’ve not heard of anyone getting infected by chlamydia, syphilis, gonorrhea, hepatitis or genital herpes via mouth contact with breasts.
As for HIV, the virus can be transmitted from mother to child via breastfeeding, via the breastmilk, but since there was no lactation in your case, you should be safe. Also, most cases of transmission via breastmilk occurs for mother to child. For an adult like you, it will be more difficult to get infected via breastmilk, even if she was lactating. This is just my guess.
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